Damascus: Army defectors killed at least eight Syrian troops on Wednesday in an act of revenge after security forces shot dead five civilians, activists said, while strikes were observed in several areas.

"At least eight soldiers were killed in an ambush on four military jeeps travelling in the village of Al-Asharna on the outskirts of (the central city of) Hama," said the Britain-based Syrian Observatory for Human Rights.

The violence comes as Western nations seek tough action against Syria at the UN Security Council, where President Bashar al-Assad's regime has support from his veto-wielding ally Russia.

On Wednesday's ambush marked the second such insurgent attack in as many days.

It was carried out by "army defectors in response to the death of five... civilians who were killed (on Wednesday) morning when their car was hit by security forces" near Al-Khataab, the Observatory said in a statement.

Three army "defectors" were wounded when they clashed with regular troops at Lujat in southern Daraa province, cradle of the revolt against Assad's 11-year rule, said the statement received in Nicosia.

"Heavy gunfire was heard in the town of Hirak," also in Daraa, which came under assault by military forces backed by tanks and troop carriers, said the rights group.

In Douma, to the north of Damascus, telephone lines were completely cut off at dawn while heavy gunfire could be heard near a state security office.

In Harasta, a suburb on the outskirts of the capital, security forces conducted raids and arrests in an assault coupled with "power-cuts in some neighbourhoods," said the Observatory.

The reports cannot be independently verified as most foreign reporters cannot enter or move freely in Syria.