Twin blasts detonated outside mosques in the northern Lebanese city of Tripoli on Friday killed 42 people, wounded more than 350 and brought major destruction in the country's second largest city, Lebanese officials said.

Footage aired on local TV showed thick, black smoke billowing over the city and bodies scattered beside burning cars in scenes reminiscent of Lebanon's 1975-90 civil war.

The blasts came amid soaring tensions in Lebanon as a result of Syria's civil war, which has sharply polarized the country along sectarian lines and between supporters and opponents of Syrian President Bashar al-Assad's regime.

Tripoli, a predominantly Sunni Muslim city, has seen frequent clashes between Sunnis and Alawites, a Shia offshoot sect to which Assad belongs. But Tripoli itself has rarely seen such explosions in recent years.

Friday's explosion also marks the first time in recent years such explosions have targeted Sunni strongholds and was bound to raise sectarian tensions in the country to new levels.

There was no immediate claim of responsibility for the attacks, which raised the spectre of Iraqi-style tit-for-tat explosions pitting Sunni against Shia.

Clerics opposed to Assad, Hezbollah safe after blasts

Security officials said the blasts went off near mosques on the Muslim day of prayer, when places of worship would be packed. An official said one of the blasts exploded outside the Taqwa mosque, the usual place of prayer for Sheik Salem Rafei, a Salafi cleric opposed to the militant Shia Hezbollah group that holds sway in much of the country. It was not clear whether he was inside the mosque, but the National News Agency said he wasn't hurt.

The official said the blast went off as worshippers were streaming out of the mosque. He spoke on condition of anonymity in line with regulations.

The second explosion went off about five minutes later in the Mina district of Tripoli, outside the Salam Mosque. The preachers of both mosques are virulent opponents of Assad and its Lebanese ally, Hezbollah.

Attacks have become common in the past few months against Shia strongholds in Lebanon, particularly following Hezbollah's open participation in Syria's civil war.

On Aug. 15, a car bomb rocked a Shia stronghold of Hezbollah in the southern suburbs of Beirut, killing 27 people and wounding over 300. A less powerful car bomb targeted the same area on July 9, wounding over 50.