A powerful explosion rocked southern Beirut on Thursday, sending smoke rising from the stronghold of the armed Lebanese Shia group Hezbollah, according to local reports.
The blast, which left at least six people dead and 66 wounded, came from a "booby-trapped car that exploded near Al-Manar's old building," the Hezbollah-controlled news network reported on its website.
Al-Manar said the explosion occurred "a few hundred meters (yards) from the politburo of Hezbollah," but added that the political office did not seem to be the target of the blast.
"This is in the heart of the Hezbollah stronghold," said Al Jazeera's Rula Amin, reporting from Beirut. "This is a very busy area, commercial and residential."
"There are a large number of people trying to get to the explosion site but security forces are trying to keep people away," Amin added. "They fear there might be another bomb, another attack."
Thursday's blast is the latest sign of heightened sectarian tensions in the country, already soaring because of the civil war in neighboring Syria.
Last week, a powerful car bomb tore through a business district in the center of Beirut, killing former Finance Minister Mohamad Chatah and five others. Former Prime Minister Saad Hariri implied that last week's explosion was linked to Hezbollah.
In November, 25 people were killed by suicide bombers at the Iranian Embassy in southern Beirut. Earlier Thursday, Lebanese authorities announced the arrest of Majed al-Majed, suspected leader of the Abdullah Azzam Brigades, an Al-Qaeda-linked group that claimed responsibility for the November attack.
Various explosions have also hit other nearby Hezbollah districts and Sunni mosques in the northern city of Tripoli.
The nature of Thursday's explosion during rush hour in the Haret Hreik neighborhood, or whether it was in retaliation, was not immediately clear.
Al Jazezera and wire services