A bomb ripped through a bus carrying civilians and military personnel during rush hour yesterday in the northern city of Tripoli, killing 18 people and wounding 46, 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 blast raised suspicions that al-Qaeda-inspired Islamic militants might have sought revenge on the military for clashes last year at a nearby Palestinian refugee camp.

But some local media speculated the blast might be aimed at undermining a visit later in the day by Lebanese President Michel Suleiman to Syria to patch up stormy relations between the neighbours the first visit by a Lebanese president to Syria in three years.

Information Minister Tarek Mitri described the incident as a ''big terrorist explosion''.

But Mr Mitri would not speculate on who was behind it.

''The hands of the criminals have hit in Tripoli against innocent soldiers and civilians,'' he told reporters in Beirut.

''Once again, they want our country to be an arena for settling scores and battling for influence.''

Shattered glass could be seen on Banks Street in Tripoli's centre. 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 had been bringing passengers from the remote northernmost Akkar region, home to many in the military.

It was riddled with shrapnel. Soldiers used sniffer dogs to search nearby parked cars, as forensic experts sifted through the wreckage. Experts determined the bomb was locally made and packed in a bag with bolts and nuts to maximise impact.

It contained 1.5kg of high-explosive TNT and was triggered by remote control, security officials said.