Najib Mikati says he is prepared to step down over car bomb attack that killed top anti-Syrian security official and seven others in downtown Beirut Reuters

Lebanon's prime minister, Najib Mikati, has offered to resign after one of the country's most senior intelligence officers was murdered in a car bomb attack that killed seven others and left scores injured in downtown Beirut.

Mikati added, however, that the country's president, Michel Suleiman, has asked him to stay on despite calls from the opposition March 14 bloc for the government to step down.

The Lebanese cabinet and security commanders held an emergency meeting on Saturday, which the state-run National News Agency said would discuss how to keep the peace.

Two protesters were wounded earlier on Saturday when the Lebanese army opened fire on a demonstartion against the bomb attack in Beirut's mainly Christian Ashrafieh neighbourhood.

"The Lebanese army were trying to open the road and started firing their guns," a witness from the village of Bar Elias, in Lebanon's eastern Bekaa Valley region, told Reuters.

Protesters have burned tyres and set up roadblocks around the country amid growing popular anger at the bombing, which threatens to spread the civil war in Syria to Lebanon.

The explosion on Friday damaged buildings across a six-blocks and was heard across much of the city, sending up a pall of black smoke above the skyline.

Many observers said the attack appeared to have links to the Syrian civil war, which is now in its 19th month. The target was Major General Wissam al-Hassan, the head of police intelligence and the prime mover behind the arrest in August of Michel Samaha, a pro-Syrian former information minister and associate of the Syrian president, Bashar al-Assad. Samaha is alleged to have been plotting a bombing campaign in Lebanon.

Hassan also led the investigation that implicated Syria and its ally Hezbollah in the killing of the former prime minister Rafik al-Hariri, according to a Lebanese official.

The killing of such a senior figure so closely linked with the anti-Assad camp in Lebanon will fuel fears that the violence in Syria is spreading to neighbouring states, including Lebanon and Turkey.

The Lebanese government has declared a national day of mourning for the victims.