BEIRUT >> Under the rattle of heavy gunfire and loud explosions, Syrian troops on Sunday regained control of a restive northwestern town, clashing with mutinous soldiers whose decision to side with armed protesters posed a potent threat to the authoritarian regime.

Backed by helicopter gunships and tanks, army units moved in after dismantling explosives planted on roads and bridges leading to Jisr al-Shughour, Syria’s state-run news agency SANA said, reporting "heavy" clashes. Residents who fled to Turkey said thousands of young men, including soldiers and police who switched sides and joined the revolt against President Bashar Assad, had armed themselves and planted dynamite at the town entrances.

Troops on Sunday removed 10 uniformed bodies from a mass grave in front of the Military Police building. At least four of the bodies were beheaded or struck on the head with an ax, according to an Associated Press reporter who was invited to accompany the Syrian forces. The building was burned and there were bloodstains in some rooms, which bolstered the reports of a mutiny last week in the town of 40,000.

Syria’s government has said 500 members of the security forces have died, including 120 last week in Jisr al-Shughour. More than 1,400 Syrians have died and some 10,000 have been detained in the government crackdown since mid-March, activists say.

Assad has made some concessions, but thousands of people demonstrating against his rule — inspired by protests in Tunisia, Egypt and elsewhere — say they will not stop until he leaves power. The mutiny in Idlib province, and the apparent willingness of some outgunned residents to stay behind and fight, was a major departure from what had been a largely peaceful protest movement.

Jisr al-Shughour’s streets were deserted at midday — residents said nearly everyone had fled in recent days — and there were piles of debris. Turkey has given sanctuary to more than 5,000 Syrians since the uprising began in mid-March, nearly all of them in the past week from the area around Jisr al-Shughour.

A resident who fled on Sunday said the army shelled Jisr al-Shughour, then tanks and other heavy armor rolled in from two directions.

As the troops advanced, he said, they fought about 60 army defectors, whose fate was unknown. He said about 200 unarmed men who were guarding the town are believed to have been either killed or detained.

The witness, who fled to an area near the Turkish border, did not give his name for fear of government reprisals.

Some Turks in the border village of Guvecci said Syrians on the other side of the frontier were calling them with reports that "smoke was rising from Jisr al-Shugour."

Residents who emerged from their homes Sunday said they were suffering before the troops came. They spoke in the presence of military officers and government officials accompanying the journalists, and it was not clear whether they expressed their views freely. Syrians who speak against the government face retribution and arrest, and few who express anti-government views will allow their names to be used.

"Gunmen were intimidating us. They told us ‘the army is coming to kill you and you have to flee the area,’" said Zeina Salloum, 37, after coming out of her home to welcome the advancing troops.

Syria-based human rights activist Mustafa Osso said the advancing troops, believed to be an elite unit led by Assad’s younger brother, fought hundreds of army defectors from the area. "This is the biggest and most dangerous wave of defections" since an uprising against Assad’s regime began in mid-March, Osso said.

There have been smaller instances of defections in the southern city of Daraa and the western town of Talkalakh, where the military conducted operations in recent weeks.

Osso said there were army operations in three parts of Idlib province including the towns of Maaret al-Numan, Jisr al-Shughour, and the nearby Jabal al-Zawiya, a mountain that includes several villages.

The province has a history of hostility to the regime. Idlib’s Muslim Brotherhood population rose up against Assad’s father, the late president Hafez Assad, in the late 1970s. Jisr al-Shughour itself came under heavy government bombardment in 1980, with a reported 70 people killed. Residents say the numbers were much higher.

The events proved a prelude to a 1982 three-week bombing campaign against the city of Hama that crushed a Sunni uprising there, killing 10,000 to 25,000 people, according to Amnesty International estimates.

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Associated Press writers Albert Aji in Jisr al-Shughour and Selcan Hacaoglu in Altinozu, Turkey, contributed to this report.