A huge car bomb exploded in a street in central Beirut during rush hour on Friday, killing at least eight people and wounding 78, witnesses and security sources said.

Lebanese officials confirmed that Wissam al-Hassan, a senior Lebanese intelligence official, was among those killed in the bombing. "Wissam al-Hassan was the target of the deadly blast and he was killed in the blast," a security source said.

Al-Hassan was the head of intelligence in Lebanon's internal security ministry, and was in line to become the head of the ministry. He was known as an opponent of the Syrian regime, and pursued elements in Lebanon that were identified with the Syrian regime.

He led the investigation that implicated Syria and Hezbollah in the killing of former Prime Minister Rafik al-Hariri in a 2005 bomb attack. He also recently led an operation that uncovered a bomb plot, leading to the arrest of a Lebanese politician known as an Assad ally.

The explosion took place a few meters away from the offices of the March 14 political group and those of the Christian Phalange party, both of which are outspoken critics of the Syrian regime of President Bashar Assad. Sami Gemayel, a Phalange lawmaker, said none of the party's members were injured.

Members of the March 14 coalition, an opposition group, were quick to point a finger at the Syrian president. “Assad has repeatedly threatened to set fire to the region if the noose tightened on him,” said March 14 coordinator Fares Soueid, according to Lebanon's Daily Star.

Former Lebanese Prime Minister Saad al-Hariri also accused Assad on Friday of being behind the bombing. Asked by Lebanon's Future Television who was responsible for the killing, Hariri replied: "Bashar Hafez al-Assad," giving the full name of the Syrian president.

Druze leader Walid Jumblatt said Hassan's death made Lebanon less safe. "He was our protector. This is a harsh blow but we will not be scared and we should not accuse anyone inside Lebanon, so we don't give Bashar an excuse to seize the country."

Several cars were destroyed by the explosion and the front of a multi-storey building was badly damaged, with tangled wires and metal railings crashing to the ground.

Residents ran about in panic looking for relatives while others helped carry the wounded to ambulances. Security forces blanketed the area.

In Washington, U.S. State Department spokeswoman Victoria Nuland condemned the blast "in strongest terms." She said the U.S. had no information about the perpetrators.

The blast occurred at a time of heightened tension between Lebanese factions on opposite sides of the Syria conflict.

The war in neighboring Syria, which has killed 30,000 people so far, has pitted mostly Sunni insurgents against President Bashar Assad, who is from the Awalite sect linked to Shi'ite Islam. Tension between Sunnis and Shi'ites has been rumbling in Lebanon ever since the end of the 1975-1990 civil war but reignited after the Syria conflict erupted.

It reached its peak when former Prime Minister Rafik al-Hariri, a Sunni, was killed in 2005. Hariri supporters accused Syria and then Hezbollah of killing him - a charge they both deny. An international tribunal accused several Hezbollah members of involvement in the murder.

Hezbollah's political opponents, who have for months accused it of aiding Assad's forces - have warned that its involvement in Syria could ignite sectarian tension of the civil war.

The last bombing in Beirut was in 2008, when three people were killed in an explosion which damaged a U.S. diplomatic car.

However, fighting broke out earlier this year between supporters and opponents of Assad in the northern city of Tripoli.