(Updated 4:10 p.m.) TRIPOLI, Lebanon - A bomb ripped through a bus carrying civilians and members of the military during Wednesday morning rush hour in the northern Lebanese city of Tripoli, killing 18 people and wounding 40, security officials said.
The officials said the dead included 10 off-duty soldiers.
The bomb was planted on the side of a main street and went off as the bus passed by. The streets were filled with people heading to work, which contributed to the many casualties, the officials said.
The military had no immediate comment. The security officials spoke on condition of anonymity because they were not authorized to speak to the media.
The blast raised suspicions that al-Qaeda-inspired Islamic militants may have sought revenge on the military for clashes last year at a nearby Palestinian refugee camp.
But some local media speculated it may be aimed at undermining a visit later Wednesday by the Lebanese president to Syria to patch up stormy relations between the neighbors.
Shattered glass could be seen in the Banks Street in Tripoli's center. Witnesses said fire engines and ambulances had rushed to the scene, while soldiers and policemen cordoned off the area to keep onlookers away and to investigate.
The small public bus, which had been bringing passengers from the remote northernmost Akkar region, home to many military members, was riddled with shrapnel from the blast.
Soldiers used sniffer dogs to search nearby parked car, as forensic experts in white uniforms, face masks and gloves sifted through the wreckage of the bus picking up evidence.
Tripoli, 90 kilometers (53 miles) on the Mediterranean coast north of Beirut, is Lebanon's second-largest city with a mostly Sunni Muslim population, dominated by groups loyal to the Western-backed parliament majority.
It has witnessed sectarian clashes between Sunni fighters and followers of the Alawite sect, an offshoot Shiite sect, in the past weeks that killed and wounded dozens of people.
The city is also close to the Palestinian refugee camp of Nahr el-Bared, which experienced deadly clashes in 2007 between Lebanese troops and members of the al-Qaida-inspired Fatah Islam group that left hundreds dead before the militants were defeated. During that fighting, the militants also were flushed out of the city.
Fatah Islam group has claimed responsibility for a bomb blast that killed a soldier in Abdeh near Tripoli on May 31.
Former Prime Minister Omar Karami