DAMASCUS: Army defectors killed at least eight Syrian troops 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 U.N. Security Council, where President Bashar Assad's regime has support from his veto-wielding ally Russia.

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.

They come a day after activists reported the deaths of at least 23 civilians across Syria at the hands of security forces seeking to crush the unprecedented protest movement that erupted mid-March.

Also on Tuesday, army defectors ambushed a Syrian security patrol, killing seven in revenge for a raid that cost 11 civilian lives, they said, while state media reported Syrian border guards shot dead two "terrorists" from Turkey.

The violence on Wednesday spilled over into neighbouring Lebanon where a Syrian military patrol entered Lebanese territory and opened fire on a border town, wounding two people, a local official said.

"Syrian troops entered Lebanese territory today and opened fire on the village of Khirbat Daoud in Aarsal," said Bakr Hujairi of Aarsal municipality.

At least three people have been killed in the area since October as Syrian troops staging incursions into Lebanon opened fire on border villages.

Meanwhile, a civil disobedience campaign was observed in parts of Syria, including the central cities of Hama and Homs, Idlib to the northwest and in Daraa, activists said.

"The second stage has begun... We will shut our mobile phones for four hours in the afternoon, block roads, and go to work without working," they wrote on their Facebook page.

The strike, which kicked off on Sunday in the name of "dignity," aims to "deprive the regime of the financial means it is using to kill our children."

A resident of Kanaker, 50 kilometres south of the capital, told AFP that "no one voted in the municipal elections," which were held on Monday.

"The strike has been ongoing since Sunday and children are not attending school," he added.

The Syrian National Council, the opposition's most representative grouping, said on its website that it is seeking new means to protect civilians from the regime's crackdown on dissent.

"The members of the Syrian National Council must discuss different ways to protect civilians. They must find new means to protect civilians in Syria," said spokeswoman Bassma Kodmani.

The unrest gripping Syria was the focus of a UN Security Council meeting on Tuesday, with UN rights chief Navi Pillay estimating more than 5,000 people have died since March in the government's crackdown on dissent.

Pillay's private briefing to the 15-nation council -- where Russia and China blocked a resolution condemning Assad in October -- heightened divisions over how to respond to the Syrian violence.

Washington has denounced the Security Council's silence on Syria as "unconscionable."

But Moscow said the West is pursuing an agenda of "regime change" by putting pressure on Syria's government but not on armed groups in the troubled country.

Pillay told reporters she had given the new toll of more than 5,000 dead -- including some 300 children -- and recommended the Assad regime's crackdown be referred to the International Criminal Court.

The Arab League has called an emergency meeting of the 22-member bloc's foreign ministers in Cairo on Saturday to respond to Syria's proposal to admit observers in exchange for an end to regional sanctions.