BAGHDAD — Under siege by government forces, al-Qaida militants tried to strengthen their hold on two of Iraq’s main Sunni cities Friday, telling residents that they were defending them against the Shiite-led government.

Iraqi troops and allied tribesmen surrounded the western city of Fallujah and fired artillery at a nearby area where up to 150 militants were stationed, a military official said, speaking on condition of anonymity as he was not authorized to release information. Troops also made forays into the city of Ramadi, he added.

Al-Qaida’s local branch, known as the Islamic State in Iraq and the Levant, have held the two cities and nearby towns in western Anbar province — the heartland of Iraq’s Sunni minority — since Wednesday, a bold move by the group, which also fights in neighboring Syria. The fighters rose up in coordinated assaults Wednesday, taking over police stations and driving out police, freeing prisoners and grabbing security forces’ vehicles.

Al-Qaida is trying to tout itself as the champions of Iraq’s Sunnis, who for the past year have been protesting against the government of Shiite Prime Minister Nouri al-Maliki, which it accuses of discriminating against their community. Their anger has further flared after authorities arrested a senior Sunni politician and dismantled a months-old sit-in in Ramadi over the past week.

To assuage Sunni anger, al-Maliki pulled the military out of an Anbar cities to give local police security duties, a top demand of Sunnis. But after the militant uprising, the military rushed reinforcements back in, supported by allied Sunni tribal fighters.

Government official Dhari al-Rishawi told The Associated Press that clashes were still under way Friday, saying the militants remain in control of Fallujah and some parts of Ramadi, Anbar’s capital. On Thursday, government warplanes fired Hellfire missiles — recently supplied by the United States — at some militant positions.

In Fallujah, al-Qaida fighters appeared at Friday prayers on the city’s main streets. One of them appealed to the worshippers for support, saying his men were there to protect them from the government, one resident told AP, speaking on condition of anonymity, fearing for his own safety.

Other fighters circulated through the city in seized police vehicles, calling out with loudspeakers, “We are your brothers from the Islamic State in Iraq and Levant. We are here to protect you from the government. We call on you to cooperate with us.”

The resident said he saw militants stationed around government buildings, and that a number of families had fled for fear of fighting inside the city, where state services have become sparse.

Fallujah and Ramadi were major strongholds for Sunni insurgents — including al-Qaida — during the U.S. presence in Iraq, when Sunnis rose up against the Americans and the government. But al-Qaida’s branch was largely defeated when many Sunni tribes turned against it and helped U.S. forces in battling it.

Many Sunni tribes remain deeply opposed to al-Qaida, even as they complain of discrimination by al-Maliki’s government.

So far, casualties from the fighting since Wednesday are not known. On Friday, two policemen were killed and six other wounded when their patrol was attacked by gunmen in speeding cars outside Fallujah, a police officer and a medical officials said on condition of anonymity as they were not authorized to release the information.

Associated Press writer Sinan Salaheddin contributed to this report.