Under the rattle of heavy gunfire and loud explosions, Syrian army troops and tanks moved into a restive north-western city from two sides Sunday, extending the crackdown on a region that is historically hostile the Damascus regime.

The Local Coordination Committees, which documents Syrian anti-government protests, said the town was attacked from the southern and eastern sides by troops in about 200 vehicles, including tanks. It said blasts were heard as helicopters clattered overhead.

The region near Turkey’s border has a history of hostility toward the Syrian regime and is posing the biggest challenge yet to President Bashar Assad’s struggle to crush the anti-government revolt. Thousands of Syrians in the region have crossed into Turkey in recent days, taking sanctuary in refugee camps.

The Syrian government has said the town was under the control of “armed men” who it said killed 120 police officers last week. Activists said the victims were killed when soldiers and police mutinied, turning their weapons on government forces.

Syrian forces told an Associated Press reporter invited to travel with them to Jisr al-Shughour that they were arresting “gunmen” in the largely evacuated city, normally home to about 40,000 people. Many of those who remained behind fled on Sunday, if they could.

The AP reporter said government soldiers took reporters into the town’s National Hospital where they saw at least two dead bodies.

The operation in al-Shughour was continuing at midday.

Syria’s state-run news agency SANA said army units entered the area after dismantling explosives planted by gunmen on roads and bridges. It added that “heavy” clashes broke out between the army units and gunmen inside Jisr al-Shughour and areas surrounding it.

Jisr al-Shughour is a predominantly Sunni town with some Alawite and Christian villages nearby in Idlib province. Most Syrians are Sunni Muslim, but Assad and the ruling elite belong to the minority Alawite sect, an offshoot of Shiite Islam.

Syria-based human rights activist Mustafa Osso said the army is conducting military operations in three areas in the Idlib province including the towns of Maaret al-Numan, Jisr al-Shughour, and the nearby Jabal al-Zawiya, a mountain that includes several village.

Osso said advancing troops, using tanks, artillery and helicopters gunships, were fighting against 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 that witnessed military operations in the past weeks.

Human rights groups say more than 1,400 people nationwide have died in the government crackdown since the uprising erupted in southern Syria 12 weeks ago.

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