BEIRUT (AFP) - Lebanese authorities on Sunday arrested members of a "terrorist network" suspected of involvement in deadly bomb attacks in the northern city of Tripoli, the army said.

"Several members of a terrorist cell involved in the recent explosions in Tripoli have been arrested," the army said in a statement carried by the official news agency NNA.

Four soldiers and three civilians were killed when an explosion ripped through a military bus in the port city on September 29. A similar attack in mid-August killed 14 people, including nine soldiers and a child.

The army said an explosives belt for use in a future attack was found during the arrest operation carried out by a joint unit of soldiers and internal security forces.

A search is underway for a leading member of the cell, named as Abdul Ghani Ali Jawhar, the statement said, adding that those arrested were questioned, without saying how many were being held.

Last year, the army fought a 15-week battle with the Al-Qaeda inspired Fatah al-Islam militia in the Palestinian refugee camp of Nahr al-Bared near Tripoli that left 400 people dead, including 168 soldiers.

An army official, declining to be named, said those arrested were Palestinian and Lebanese but without specifying if they were Islamists. The arrests were carried out near Baddawi, another Palestinian camp.

Security sources told AFP that a total of six people were detained, including four men from the same family: Mahmud Azzam, 80, and his three sons. The father and two of his sons were released after questioning.

One son had returned the previous day from Denmark, another from Algeria and the third worked in Lebanon, one of the sources said, adding that they were from Nahr al-Bared.

A fourth brother, Jihad, had been killed in last year's fighting with the army, the sources said.

A Lebanese man, Alaa Mehrez, also known as Attiya, was detained in possession of the explosives belt as well as a woman who was with him at the time in the mainly Sunni district of Bab el-Tebbaneh, the sources said.

They said Mehrez was a brother-in-law of the main suspect on the run.

Tripoli has also since May also been rocked by deadly sectarian violence between Sunni supporters of the government and their Damascus-backed rivals from the Alawite community.