NAHR AL-BARED, Lebanon - Troops on Sunday bombarded the north Lebanon Palestinian refugee camp of Nahr al-Bared in a bid to smash underground bunkers sheltering Fatah al-Islam fighters, who killed two more soldiers at the weekend.

An AFP correspondent saw military helicopters drop nine bombs on a section of the camp from where the intermittent sound of gunfire could also be heard.

A military spokesman said the bombs were 400-kilogram (880-pound) ones which had been used for the first time on Saturday, instead of the 250-kilo bombs used almost daily since it began using air power on August 9.

At the same time, Lebanese tanks poured a steady stream of shells into the Islamists' position, the noise of explosives punctuated by the clatter of automatic gunfire from within the camp.

"One soldier was killed on Saturday evening, and another who was wounded at the same time died on Sunday," the military spokesman said.

He told AFP that the army's firepower gave them "control of the zone held by the Islamists, but that the troops had to clean up the terrain before being able to advance."

The military estimates that the Islamists who have been fighting since May 20 now number only around 70 gunmen but that they are holed up "in five or six well-equipped shelters."

Much of the camp, like Lebanon's other Palestinian refugee camps, was reinforced and given underground shelters and tunnels to withstand possible air raids by the Israeli military.

Most of Nahr al-Bared's 31,000 refugee-residents fled at the start of the fighting, with just the wives and children of the Islamists remaining -- a total of about 100 who the army says are being used as "human shields" by those holding out.

More than 100 people suspected of belonging to Fatah al-Islam have been arrested since the Islamists began fighting the Lebanese army in May, a legal official said on Sunday.

In the three months of fighting more than 200 people have been killed, including, with the latest two deaths, 138 soldiers. It is not known how many Islamists have died.

Some of the people detained will face murder charges, the official said, while others will be charged with belonging to the extremist group.

"The number of detainees has passed the 100 mark. They involve mainly Lebanese, as well as some Palestinians, Saudis, Syrians and a small number of people of other nationalities," the official told AFP on condition of anonymity.

He said those arrested would be tried by a civilian court and that files on the suspects had been given by the military to Lebanon's state prosecutor Said Mirza, who was preparing to start prosecuting early this week.

The fighting erupted three months ago when the Islamists launched a series of attacks around Nahr al-Bared and killed 27 soldiers.

Some of those now being held were detained in the nearby main town of Tripoli, while others were seized trying to flee the besieged camp. -AFP