Beirut ? Syrian security forces fired on anti-government protests Friday and conducted sweeping raids during violence that killed at least 16 people, activists said.

With more than 250 Syrians killed in less than two weeks, November is shaping up to be one of the bloodiest months yet in a dramatic escalation of the conflict around Syria’s 8-month-old uprising. There have been growing signs that some protesters are taking up arms to protect themselves, along with reports of intense battles between soldiers and army defectors.

The bloodshed came as Human Rights Watch accused the regime of possible crimes against humanity in the crackdown that the U.N. estimates has killed at least 3,500 since the uprising began in mid-March.

The Arab League is to meet at its Cairo headquarters Saturday to discuss the failure by President Bashar Assad’s regime to abide by a deal to stop the violence. Damascus agreed to the Arab League-brokered plan last week, but the violence only accelerated as regime troops launched an assault to crush resistance in Syria’s third-largest city, Homs.

New York-based Human Rights Watch urged the 22-member league to suspend Syria’s membership. “The Arab League needs to tell President Assad that violating their agreement has consequences, and that it now supports (U.N.) Security Council action to end the carnage,” said Sarah Leah Whitson, Middle East director at Human Rights Watch.

Friday saw a repeat of the cycle that has characterized Syria’s results — mass protests after weekly Muslim prayers in areas around the country, met with swift and deadly crackdowns by security forces. At the same time, security forces raided homes in Homs, hunting for activists.

In addition to ongoing military operations in Homs, activists said fierce clashes were taking place Friday in the northern town of Khan Shaikhoun near the Turkish border between the military and gunmen believed to be army defectors.

The two main Syrian activist groups reported at least 16 deaths, 10 of them in Homs.

The deaths were the latest in a particularly bloody month so far. One of the groups, the Local Coordinating Committees, said 250 Syrians have been killed since the start of November, most of them civilians with about 20 soldiers.

The British-based Syrian Observatory for Human Rights also documented more than 200 deaths. But the observatory has a far higher toll for soldiers, saying more than 100 were killed.

The differing death tolls could not be immediately reconciled. The government has largely sealed off the country from foreign journalists and prevented independent reporting, making it difficult to confirm events on the ground.

On Friday, Human Rights Watch said Syrian forces have tortured and killed civilians in Homs province — where the besieged city is located — in an assault that indicates crimes against humanity.