BEIRUT — A car bomb ripped through a Shiite neighborhood in southern Beirut on Tuesday, 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 neighborhood of Haret Hreik this month amid a series of attacks that have shaken Lebanon in a spillover of Syria's civil war into its smaller neighbor.

The violence has targeted both 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 on opposing sides of the war.

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 in the explosion.

A group known as Al-Nusra Front in Lebanon claimed responsibility for 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, speaking on condition of anonymity because he was not authorized to talk to the media, said the car was stolen and was packed with 20 kilograms (44 pounds) 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.

On Thursday, a car bomb struck the northeastern Shiite town of Hermel close to the Syrian border during rush hour, killing at least three people and wounding more than 20.

And on Jan. 2, a bombing took place in Haret Hreik, just meters (yards) from where Tuesday's attack occurred, killing five people.

Other attacks in Lebanon include a twin car suicide bombing that targeted the Iranian embassy in an upscale Shiite neighborhood in November, killing at least 23 people. Iran is the chief patron of Hezbollah and an ally of Syria, and the Islamic Republic's embassy is located in a Shiite district.

Another bombing, in August, killed around 20 people in the Beir al-Abed neighborhood, which is near Haret Hreik.

Other attacks have targeted Lebanon's Sunni community, including two car bombs that targeted worshippers at a mosque in the northern Lebanese city of Tripoli in August, killing scores. A December car bombing in Beirut killed prominent Sunni politician Mohammed Chatah.

Shortly after Tuesday's bombing, clashes broke out in the northern Lebanese city of Tripoli, killing at least one person, said the security official. The city, with impoverished rival Sunni and Shiite areas, has seen frequent sectarian clashes linked to the war Syria that have killed dozens.

The flattest ighting unraveled a tenuous truce that had taken place just earlier in the morning, following clashes that broke out between the rival neighborhoods on Saturday.