TRIPOLI, Libya — One thousand rebels bombarded buildings filled with regime fighters hiding amid civilians in a ferocious battle today for Moammar Gadhafi’s last major stronghold in Tripoli. The Libyan leader, still in hiding, sent a new message calling on his supporters to kill the rebels.

The bullet-riddled bodies of three Gadhafi soldiers in military uniforms lay on the ground outside a fire station in the battle-scarred Abu-Salim neighborhood and a few bodies of rebel soldiers were wrapped in blankets nearby. The gutters ran red with blood.

Deafening explosions of outgoing mortars and the whistle of sniper fire filled air clogged with smoke from burning buildings and weapons fire. A mother ran out of one the buildings under siege, screaming for first aid for her wounded son. Behind her, the building’s glass windows were shattered and black smoked poured out of a burning apartment. Amid the din, the call to prayer wafted out from neighborhood mosques.

Mahmoud Bakoush, a rebel commander at the site, said there were rumors that one of Gadhafi’s sons might be in the buildings, but that was not confirmed. The battles raged for at least four hours, then stopped at sundown.

Abu Salim, which is adjacent to Gadhafi’s Bab al-Aziziya compound seized by rebels on Tuesday, is thought to be the last major hotbed of regime brigades in Tripoli. After hours of fierce fighting, Associated Press reporters at the scene said rebels were making progress pushing them out. Many of the fighters are believed to have moved to Abu Salim from Bab al-Aziziya after the compound was captured and ransacked.

The rebels are struggling to take complete control of Tripoli, four days after they swept into the capital and sparked the collapse of Gadhafi’s regime. The autocrat has refused to surrender and has vowed from hiding to fight on “until victory or martyrdom.” The rebel leadership has offered a $2 million bounty on Gadhafi’s head.

The rebels know they will not be able to declare a full victory in the 6-month-old civil war until Gadhafi is either captured or killed.

“Don’t leave Tripoli for the rats. Fight them, fight them, and kill them,” Gadhafi said in audio message broadcast on Al-Rai television. “It is the time for martyrdom or victory,” he said, calling tribes outside the capital “to continue their march to Tripoli.” He said imams in mosques should call for youths to rise up “for jihad.”

He warned the rebels will enter people’s homes and rape their women. “They will enter your houses and deprive you of your honor,” he said. “NATO can’t remain in the air all the time.”

A regime spokesman told the AP Gadhafi is safely in hiding and leading the battle against the rebels. Moussa Ibrahim, in a call to AP’s Cairo office, said the longtime dictator was in Libya and his morale was high. Gadhafi “is indeed leading the battle for our freedom and independence” said Ibrahim, who was recognizable by his voice.

Ibrahim refused to say where Gadhafi was hiding. Ibrahim, who had for months appeared daily in televised news conferences since the start of the rebellion six months ago, added he himself was in an undisclosed location in Libya and constantly on the move.

“All of the leader’s family are fine,” Ibrahim said, adding that top military and political aides remained with Gadhafi. He said Gadhafi was capable of continuing resistance for “weeks, months and years.”

Ibrahim claimed Gadhafi’s forces controlled a “good portion” of the capital — a claim that contradicts what reporters are seeing on the ground.

In Abu Salim, rebels in pickup trucks with anti-aircraft guns mounted on the back were hammering blocks of low-rise, four and five story buildings with anti-aircraft fire, machine guns, and rocket-propelled grenades. Gadhafi forces responded with mortars and dynamite.Huge explosions filled the air continually, as buildings burned. Empty bullet-casings coated the streets.

“They are holding at least 10 tall buildings. They have heavy weaponry, maybe even a tank,” Mohammed Karami, a rebel involved in the battle, said of the Gadhafi loyalists.

A hospital in the middle of the battlefield was scorched and a fire station completely destroyed with the bullet-ridden bodies of three dead Gadhafi soldiers in the yard.

Rebels were hauling away prisoners, some of them with an African appearance — possibly mercenaries who have been defending Gadhafi.

In another part of Tripoli, a separate gunbattle erupted outside the Corinthia hotel, where many foreign journalists are staying. About a dozen rebels with machine guns and an anti-aircraft gun fired on what appeared to be loyalist gunmen shooting from nearby high-rise buildings.

In Washington, the Pentagon pushed back on assertions today that either NATO or the U.S. military is actively engaged in a manhunt for Gadhafi, underscoring ongoing sensitivities over the strict parameters of the U.N. mission there.

Marine Col. David Lapan said the U.S. is conducting aerial surveillance of Libya in support of NATO’s military mission to protect civilians from attack by government forces. But he said this does not amount to targeting Gadhafi, whose exact whereabouts are unknown.

He said it is not NATO’s mission to target or hunt down individuals.

That statement conflicted with comments by British Defense Secretary Liam Fox, who said today that NATO intelligence and reconnaissance assets are being used to try to hunt down Gadhafi.

Rebels say one of their key targets now is Gadhafi’s hometown of Sirte, about 250 miles (400 kilometers) from Tripoli, but acknowledged that capturing that city would not be easy because Gadhafi’s fellow tribesmen were expected to put up a fierce fight. Opposition leaders have said they were trying to negotiate a peaceful surrender of the city.

Mustafa Abdel-Jalil, head of the rebel National Transitional Council, called on people living in loyalist-held towns to join the fight against Gadhafi’s soldiers.

“I am appealing to the areas not yet liberated to join the revolution,” he told reporters in Benghazi. “There is no excuse for them not to join.”

Fawzi Abu Ketf, deputy defense minister of the rebel National Transitional Council, said fighting was raging today outside Bin Jawad, 400 miles (650 kilometers) south of Tripoli. Gadhafi loyalists ambushed rebels advancing toward the city on Wednesday, killing at least 20 of them.

Wednesday’s attack was carried out by pro-Gadhafi forces who had retreated from the oil city of Ras Lanouf after rebels captured that city earlier this week, said Ahmed Zeleity, a rebel commander.

The ambush showed that pro-regime forces retain the ability to strike back even as the rebels tighten their control over the nation’s capital.

Rebels also have seized several parts of Sebha, another Gadhafi stronghold still holding out, including the main commercial Gamal Abdel-Nasser street, according to rebel official Adel al-Zintani, who is in daily telephone contact with rebel commanders in the desert city.

He said mercenaries from sub-Saharan African nations who had been paid by Gadhafi have fled the city, but loyal soldiers were continuing to hold firm.

Ketf said another challenge was the need to supply troops at the front.

“The supply lines will be too long and we are short of funds and supplies,” he said.

The humanitarian situation there is increasingly difficult, he said, with lengthy power and water outages.

In Milan, Italian Premier Silvio Berlusconi said Italy was preparing to release $505 million in frozen assets in Italian banks, calling it the first payment. Italy, Libya’s former colonial ruler and biggest trading partner, has not disclosed the total Libyan assets held there.

Berlusconi made the announcement after meeting with the leader of Libya’s rebel Cabinet, the second stop on a European diplomatic tour by Mahmoud Jibril aimed at securing the release of billions of dollars in frozen Libyan assets.

The Libyan opposition says they urgently need at least $5 billion of those assets to pay state salaries, maintain vital services and repair critical oil facilities.

The U.N. Security Council, meanwhile, is preparing to vote this week on a resolution that would release $1.5 billion in Libyan assets in U.S. banks that the world body froze to thwart Gadhafi. Analysts estimate as much as $110 billion is frozen in banks worldwide.

Reflecting the continuing unrest in parts of Libya, a Maltese ship sent to evacuate foreigners from Tripoli turned back today after fighting in the Libyan capital made the operation too risky. The vessel was to evacuate at least 24 foreigners trapped in the Libyan capital, but the Maltese government said the mission was aborted today after it became impossible for people to reach the harbor due to fighting in the capital.

The Geneva-based group the International Organization for Migration, however, said a ship chartered to rescue hundreds of foreigners in Tripoli had managed to dock there, after waiting offshore for days due to fighting.

The group is “very optimistic that we will be able to carry out the evacuation today,” spokeswoman Jemini Pandya said.

Four Italian journalists taken at gunpoint in Libya were freed in a raid on the house where they were being held, an official said. The four were taken at gunpoint Wednesday by forces loyal to the regime of fugitive Libyan dictator, Moammar Gadhafi. Their Libyan driver was killed.