A military helicopter flies over Daria, near Damascus, in July. Syrian state TV has reported the crash of a military helicopter over Damascus on Thursday. (Shaam News Network/Reuters)

A Syrian military helicopter crashed after it clipped the tail of a Syrian passenger jet with 200 people aboard in mid-air, but the larger aircraft landed safely and no one aboard was hurt, Syria's state TV says.

The helicopter crashed near the capital of Damascus, though it was not clear if there were any casualties or what had led the two aircraft to touch in mid-air.

The close call came at a time when Syria is embroiled in a civil war between the supporters of President Bashar al-Assad and those trying to topple him. The 18-month rebellion has claimed the lives of more than 23,000 people, according to activists, and Syria has descended into chaos.

The Syrian government has increasingly been using helicopters and other aircraft in its fight against the rebels. Rebels have claimed to have shot down helicopters and warplanes in the past, although the regime has blamed most of the problems on mechanical difficulties.

In Thursday's incident, the helicopter's rotor clipped the tail of a Syrian Arab Airlines jet, state TV said. The passenger plane "landed safely at the airport and none of the 200 passengers were harmed," the report said.

The helicopter crashed southeast of Douma, a Damascus suburb that has witnessed repeated military crackdowns to purge fighters seeking to topple Assad. No further details were made available.

"We heard the sound of several explosions and some gunfire, and a few minutes later, we were told that a helicopter had crashed," said Mohammad Saeed, an activist in Douma.

Airstrike hits gas station in northern Syria

Meanwhile, in northern Syria, opposition activists said a regime airstrike hit a gas station Thursday, setting off an explosion that killed at least 30 people and wounding dozens more.

The explosion went off in the town of Ain Issa, about 40 kilometres from the Turkish border, said Rami Abdul-Rahman of the Britain-based Syrian Observatory for Human Rights. Abdul-Rahman said witnesses told him they saw at least 30 bodies, but that the death toll was likely to rise. He said dozens of people were wounded.

Abdul-Rahman quoted one witness as saying the blast was caused by an airstrike, but that the Observatory could not independently confirm the cause of the explosion.

Another group of anti-regime activists, the Local Co-ordination Committees, reported intense attacks by warplanes on the gas station.

The group did not give a death toll, saying only that many people were killed or wounded. It said more than 70 wounded people were taken to a hospital in the provincial capital of Raqqa.

Army raid on Palestinian refugee camp

Earlier in Damascus, soldiers raided a Palestinian refugee camp where many Syrians from other parts of the country's capital and its suburbs have been sheltering, arresting dozens of people in a sweeping operation, the government and opposition groups said.

Syrian TV said an army unit conducted a "special operation" during which about 100 gunmen were captured in the Palestinian refugee camps of Yarmouk and Palestine in Damascus. It gave no further details.

The Local Co-ordination Committees activist network reported gunfire and several casualties that accompanied the raid. The British-based Syrian Observatory for Human Rights said three people were killed and dozens of others were arrested when troops stormed parts of the Yarmouk camp that has provided shelter for many residents of Damascus's Hajar al-Aswad district, an area has seen heavy fighting between rebels and government troops in recent days.