BEIRUT – Bullets and shells smashed into homes in the Syrian capital of Damascus overnight as rebels took their fight against President Bashar Assad to the center of his power.

In nearly 12 hours of fighting that lasted into the early hours Saturday, rebels armed mainly with assault rifles clashed with Syrian forces in the heaviest fighting in the Assad stronghold since the 15-month-old uprising began. U.N. observers said rebels fired a rocket-propelled grenade at the local power plant, damaging parts of it and reducing six buses to charred shells.

Syrian forces showed the regime’s willingness to unleash their firepower in the capital, as at least three tank shells slammed into residential areas in the central Damascus neighborhood of Qaboun, an activist said.

DEATHS OUTSIDE DAMASCUS

At least 52 civilians were killed around the country outside Damascus on Saturday, according to the Syrian Observatory for Human Rights, a Britain-based activist group.

Among them were 20 people, including nine women and children, who died in heavy pre-dawn shelling in the southern city of Daraa, where the uprising against Assad began in March 2011. Six children were among 10 killed by a shell that exploded in a house they took cover in during fierce fighting in the coastal region of Latakia, the group said.

The group’s figures could not be independently confirmed.

In a Daraa mosque, a father stood over his son killed in the shelling, swaddled in a blanket and a hooded sweater, amateur video showed. “I will become a suicide bomber!” the father shouted in grief.

Another video showed tens of thousands of Daraa residents burying their slain victims later Saturday — singing, dancing and parading the dead in coffins around a large square and giving the mass funeral the appearance of a mass wedding party.

The Damascus violence was a dramatic shift; the capital has been relatively quiet compared with other Syrian cities throughout the uprising. Damascus and the northern city of Aleppo, the country’s largest, are under the firm grip of security forces.

The rebels’ brazenness in the Damascus districts underscored deep-seated Sunni anger against the regime, with residents risking their safety to shelter the fighters. Residents burned tires to block the advance of Syrian troops, sending plumes of smoke into the air, amateur video showed.

Urban Sunni Syrians had once mostly stayed at arm’s length from their mostly rural compatriots leading the uprising, fearing the instability that their leaderless, chaotic movement would bring.

But it appears a series of massacres of mainly Sunni peasants over the past few weeks have tipped some of their urban brethren in favor of the uprising. One rebel supporter in Qaboun said the recent mass killings made people see rebel fighters more as protectors against Assad’s forces.

“The regime has forced the rebels into the city. When they commit attacks, or massacres, or arrests, they come in to defend residents,” he said.

REVOLT GATHERS STRENGTH

The most recent mass killing took place Wednesday in central Syria, where activists say up to 78 people were hacked, burned and stabbed in the farming village of Mazraat al-Qubair. The opposition and regime have traded blame over the slayings.

“The heart of this revolt is the poor, jobless youth in the countryside. But that is gathering strength in other places, in Aleppo, in Damascus and even the Kurdish regions,” said Syria expert Joshua Landis.

“The psychological state of the people, after watching these massacres, is so far advanced. People are ready to do whatever it takes. They are frightened; it could come next to them.”

The fighting began in two neighborhoods, Qaboun and Barzeh, during the day Friday, when troops opened fire on anti-Assad opposition gatherings and rebels responded, witnesses said. Blasts shook the districts until about 1:30 a.m. Saturday. In the fringe neighborhood of Kfar Souseh, fighting began after rebels attacked a Syrian forces checkpoint. At least five people were killed in Qaboun, according to an activist video that showed the bodies.

Also Saturday, troops shelled parts of the central city of Homs, one of the main battlegrounds of the uprising, and stormed into the city’s posh neighborhood of Ghouta, conducting raids.

The latest escalations are another blow to international envoy Kofi Annan’s peace plan, which aims to end the country’s bloodletting. Annan brokered a cease-fire that went into effect on April 12 but has since been violated nearly every day.

Thousands have been killed since the crisis began in March last year. The U.N.’s latest estimate is 9,000 dead, but that is from April and it has been unable to update it. Syrian activists put the toll at more than 13,000.

Efforts by Western and Arab nations to help the opposition have been hampered by fragmentation amid the movement. The main opposition movement, the Syrian National Council, has been plagued by infighting.