BEIRUT - Elite Syrian troops backed by helicopters and tanks regained control Sunday of a town where police and soldiers joined forces with the protesters they were ordered to shoot -- a decisive assault from a government prepared for an all-out battle to keep power.

Troops led by the president's brother shelled Jisr al-Shughour as the gunships hovered overhead, paving the way for scores of tanks and armored personnel carriers to roll in from two directions. By early afternoon, the sounds of battle faded. The army was in control.

Sunday's developments, and actions by opponents of the Syrian government, marked a major departure from what had been a largely peaceful protest movement. Among them: the discovery of a mass grave filled with uniformed bodies and the increasing willingness of mutineers and outgunned residents to fight back.

President Basher Assad's response in Jisr al-Shughour, the first town to spin out of government control since the uprising began in mid-March, mirrored his father's 1980 assault there. It was a clear message to anyone contemplating defiance.

Syrians who were among thousands to flee for the nearby Turkish border said about 60 mutineers were defending the town alongside some 200 unarmed residents. Their fate was unknown late Sunday, but the government reported three deaths in the fighting -- one of its own soldiers and two unidentified men whose bodies were shown to reporters.

"The Syrian army is fighting itself," said Muhieddine Lathkani, a London-based Syrian writer and intellectual. "The army's response was strong because they did not want the mutiny to become larger."

Neighboring Turkey, about 12 miles (20 kilometers) away, has given sanctuary to more than 5,000 fleeing Syrians, nearly all of them in the past few days from Idlib province. Turkey's prime minister has accused the Assad regime of "savagery."

Arab governments, which were unusually supportive of NATO intervention in Libya, have been silent in the face of Syria's crackdown, fearing that the alternative to Assad would be chaos. The country has an explosive sectarian mix and is seen as a regional powerhouse with influence on events in neighboring Israel, Lebanon, Iraq.

Fridays in Syria have become a familiar cycle of protest and government crackdown, one that appeared likely to continue on June 3 in Jisr al-Shughour and elsewhere. Instead, residents say, police and soldiers turned on their commanders, and control of the town slipped out of government hands.