BEIRUT: An explosion struck a gas pipeline Tuesday in central Syria in an attack the government blamed on terrorists, the state-run news agency said. There were no casualties.

The blast happened near the town Rastan in the restive Homs province, SANA reported.

There have been several pipeline attacks since the Syrian uprising began in mid-March, but it is not clear who is behind them at a time when violence across the country is spiraling out control, unearthing long-standing grievances and resentments.

The government blames saboteurs and terrorists for the blasts.

But the opposition accuses the regime of playing on fears of religious extremism and terrorism to rally support behind President Bashar Assad, who has portrayed himself as the only force that can stabilize the country.

Syria has banned most foreign journalists from the country and prevented independent reporting, making it difficult to confirm claims from either side.

On Monday, the head of the Arab League said Syrian security forces are still killing anti-government protesters despite the presence of foreign monitors in the country.

But he insisted the observer mission has yielded important concessions from the Damascus regime, such as the withdrawal of heavy weapons from cities.

Opposition groups have been deeply critical of the mission, saying it is simply giving Assad cover for his crackdown.

"The Arab League has fallen victim to the regime's typical traps, in which observers have no choice but to witness regime-staged events, and move about the country only with the full knowledge of the regime," said a statement by the Local Coordinating Committees, an umbrella group of activists.

"This has rendered the observers unable to work or move independently or in a neutral manner," the group said.

The U.N. estimates more than 5,000 people have been killed since the revolt erupted in mid-March. Activists say that in the week since the observers started their work in Syria on Dec. 27, hundreds have been slain. The LCC put the death toll at more than 390 people since Dec. 21.

"Yes, there is still shooting and yes there are still snipers," Arab League Secretary-General Nabil Elaraby told a news conference in Cairo on Monday. "Yes, killings continue. The objective is for us to wake up in the morning and hear that no one is killed. The mission's philosophy is to protect civilians, so if one is killed, then our mission is incomplete."

"There must be a complete cease-fire," Elaraby said.

Elaraby stressed the achievements of the Arab League mission, saying Syria's government has pulled tanks and artillery from cities and residential neighborhoods and freed some 3,500 prisoners. He said food supplies have reached residents and the bodies of dead protesters have been recovered.

The monitors are supposed to verify Syria's compliance with an Arab League plan to stop the crackdown on dissent - a plan Syria agreed to on Dec. 19. The plan requires Assad's regime to remove security forces and heavy weapons from city streets, start talks with opposition leaders and free political prisoners.

The ongoing violence is reinforcing the opposition's view that Syria's limited cooperation with the observers is nothing more than a ploy by Assad's regime to buy time and forestall more international condemnation and sanctions.

In its statement, the LCC said the regime has been disguising soldiers and army officers in police uniforms and hiding their army vehicles to make it appear they have pulled out in accordance with the Arab League plan.

While most of the violence reported early in the uprising involved Syrian forces firing on unarmed protesters, there are now more frequent armed clashes between military defectors and security forces. The increasing militarization of the conflict has raised fears the country is sliding toward civil war.

The LCC said 20 people were killed across the country Monday, including 11 in restive Homs province in central Syria and three in Idlib province, which borders Turkey.