At least four people died when a car bomb ripped through a Shiite neighbourhood in southern Beirut (AP)

A car bomb has ripped through a Shiite neighbourhood in southern Beirut, killing four people and sending plumes of smoke over the area in the latest attack targeting supporters of Lebanon's militant Hezbollah group.

It was the second bombing in the Haret Hreik neighbourhood this month in a series of attacks that have shaken Lebanon as Syria's civil war spills over into its smaller neighbour.

The violence has targeted Lebanon's Sunnis and Shiites and has further stoked sectarian tensions that are already running high as each Lebanese community lines up with its brethren in Syria.

As the car bomb went off, thousands of people flocked to the southern Beirut district. Footage broadcast by the Hezbollah-owned al-Manar television station showed medics hauling a man on a stretcher out of the area as flames engulfed a building and debris littered the busy commercial street.

The Lebanese Red Cross, in a statement to the state-run National News Agency, said that along with the four killed, 35 people were wounded.

A group known as Al-Nusra Front in Lebanon claimed the attack, saying it was in retaliation for Hezbollah's military support of president Bashar Assad's forces in Syria.

The claim was posted on the group's Twitter account. Its name suggested ties to the al Qaida-linked Nusra Front in Syria, one of the most powerful Sunni militant brigades fighting Assad's troops and their allies.

Lebanon's official media said a suicide bomber in a vehicle was behind the attack. A security official said the car was stolen and packed with 44lb of explosives.

"There was a car beeping, and then it exploded," an unnamed eyewitness told the Voice of Lebanon radio station. "Then we saw people on the ground - like every time."

Similar attacks have targeted Shiite areas in Lebanon in recent months in retaliation for the Shiite Hezbollah fighters' role in the civil war next door where Assad's forces are battling chaotic bands of Sunni rebels, including extremists fighters linked to al Qaida.

While Lebanon's Shiites have broadly supported Assad's rule, the country's Sunni community generally aides their brethren in Syria and shadowy Sunni groups - such as the Al-Nusra Front in Lebanon - have sought to punish Lebanon's Shiites.

PA Media