Forensic experts search for evidence in the bus wreckage at the site of the explosion in the northern Lebanese city of Tripoli. (Ahmad Omar/Associated Press)A car bomb killed several Lebanese troops riding on a bus into the port city of Tripoli in northern Lebanon on Monday, security officials said.

At least five people were killed and 25 injured in the explosion that is believed to have been remotely detonated.

Police dressed in plain clothes were on the scene investigating the wreckage of a white Nissan minibus that was being used to transport the soldiers, said CBC reporter Nahlah Ayed. The vehicle was pockmarked with shrapnel and had its tires blown out in the explosion.

A car packed with explosives mixed with metal balls was parked on the side of a road and detonated as the bus drove by in the Bahsas neighbourhood at the southern entrance of the city.

The explosion damaged surrounding cars and nearby buildings, Ayed said. Shattered glass lined the road.

Four soldiers were among the dead and 22 of the injured were also troops, a senior military official told the Associated Press.

Lebanese police secure the area after an explosion that killed five and injured 25. (Associated Press)It was the second deadly attack targeting troops in northern Lebanon in less than two months.

On Aug. 13, 18 soldiers and civilians were killed by a roadside bomb near a bus carrying troops on a busy Tripoli street. It was Lebanon's deadliest bombing in more than three years.

Tripoli — Lebanon's second-largest city, 60 kilometres north of Beirut on the Mediterranean coast — is a majority Sunni city. It has been rocked by sectarian fighting between pro-government Sunni fighters and pro-Syrian gunmen of the Alawite sect.

Monday's explosion also came two days after a massive bombing in the capital of neighbouring Syria killed 17 people and wounded 14.

Syrian authorities on Monday said the attack was carried out by a suicide bomber and that the vehicle came from a neighbouring Arab country.

The region there is known to be a strong base for Sunni militants.

Sheik Daie al-Islam al-Shahal, founder of the fundamentalist Salafi Sunni movement in northern Lebanon, said Monday's attack was part of the conflict among "external forces" in Lebanon and rejected suggestions that Sunni militants were behind it.

"The false allegations and haste do not help stability and cause tensions," said al-Shahal, Lebanon's most powerful Salafist leader.

With files from the Associated Press