Four army personnel, including an officer, were killed Thursday by armed groups in Syria's central province of Homs, state-run SANA news agency reported.

Lieutenant Colonel Ammar al-Jurf, Chief Warrant Officer Tarek Suleiman and another two law-enforcement officials were killed in clashes with armed groups in al-Qassir town in Homs' countryside, said SANA.

Meanwhile, some armed groups set up roadblocks in the streets of Homs and set tires on fire, while some others broke into stores and houses and stole their contents, said SANA, adding that the authorities had discovered trenches used by "terrorists" in their attacks against civilians and law-enforcement forces.

Seven mortar shells were fired Thursday at the a refinery in Homs by gunmen within five hours, SANA said.

In southern Daraa province, government forces raided Thursday a house in Taseel town, seizing 14 boxes of mines, 6 boxes of TNT charges, 2,000 meters of detonating fuse, 32 anti-tank mines, 7 boxes of ammunition, 2 boxes of MD detonators and a box of electrical detonators, according to SANA.

The forces also seized a hand-made rocket, 20 explosive devices, cylinders primed for explosion, a stolen car and some automatic weapons, it added.

In northern Idlib province, an armed group detonated an explosive device under a railway bridge west of Ma'ardes village, damaging the bridge without causing human losses.

On the other hand, the Britain-based Syrian Observatory for Human Rights reportedly said that around 63 people were killed in Homs Thursday, as the Local Coordination Committees (LCC) put the number of killed at up to 100.

The opposition's account could not be independently verified.

Syria blames the unrest on armed groups backed by a foreign conspiracy with the aim of toppling the regime of Syrian President Bashar al-Assad.

Syrian forces have stepped up their crackdown over the past week on armed groups in restive areas in central Syria and suburbs of the capital Damascus.

The Syrian government said more than 2,000 army and security personnel have been killed during the months-long unrest, while the United Nations put the death toll in the country at more than 5,400.