Twin car bomb explosions have killed at least 42 people outside two Sunni mosques in the northern Lebanese city of Tripoli.
Footage aired on local television showed think, black smoke billowing over the city, with bodies lying by burning cars, reminding the country of its 1975-90 civil war.
The explosions came amid rising tensions in Lebanon resulting from neighbouring Syria's civil war, polarising the country along sectarian lines and between supporters and opponents of President Bashar al-Assad's regime.
This incident was the second such bombing in just over a week, showing the extent to which the country is being caught up in its neighbour's war.
Tripoli has previously seen clashes between Sunnis and Alawites, a Shiite offshoot sect to which Mr Assad belongs. But such violent explosions have been rare in recent years, with Friday's blasts marking the first time in years that such attacks have been made on Sunni areas. These were also the deadliest explosions in Tripoli since the civil war came to an end.
One of the blasts occurred outside the Taqwa mosque, where Sheik Salem Rafei, a Salafi cleric opposed to Lebanon's militant Shiite Hezbollah group, usually worships. It is not yet clear whether he was inside. According to accounts earlier in the day at leat 14 people were killed.
The second device went off roughly five minutes later in the Mina area of Tripoli near to the front gate of the Salam Mosque, making a 5 metre-wide crater outside. Video footage obtained by local news channel LBC shows how the explosion ripped through a wall of the mosque, showering people sitting on prayer mats with clouds of dust
The explosions were set to go off during Friday prayers.
The imams of both mosques are outspoken opponents of Mr Assad and Hezbollah.
There has been no claim of responsibility for Friday's attacks, which raised the grim possibility of 'tit-for-tat' sectarian fighting between Sunnis and Shiites that has blighted Iraq since the 2003 invasion.
Hezbollah has condemned the bombings, calling it a "terrorist bombing" and part of a "criminal project that aims to sow the seeds of civil strife between the Lebanese and drag them into sectarian and ethnic infighting." The group released a strongly worded statement expressing, "utmost solidarity and unity with our brothers in the beloved city of Tripoli."
The U.S. Embassy in Lebanon has condemned the bombings and called on all parties to exercise calm and restraint.
Additional reporting by AP and Reuters