Sporadic gunfire exchanges have continued daily since the truce halted three days of heavy fighting. But the renewed fighting before sundown, with the Lebanese army using artillery to silence the militants' source of fire, was the worst outbreak in violence in a week.
Lebanese army artillery pounded positions on the northern edge of the camp and near the Mediterranean coastline, apparently seeking to prevent any attempt by some militants to flee by sea.
The renewed fighting came hours after a soldier was killed. The soldier was hit in the head by sniper fire Monday afternoon and later died in a hospital, said security officials, speaking on condition of anonymity because they were not authorized to speak to the media.
In Beirut, a man suspected of belonging to Fatah Islam was arrested after police raided the apartment where he was staying in a posh furnished building in Ashrafieh, a Christian neighborhood in the heart of the Lebanese capital.
Police officials said the man had rented the place using a forged Lebanese name and passport and had in his possession several other forged passports from Gulf and other foreign countries. They said police also confiscated from the apartment several CDs and other material that appeared to be related to the group's work.
Also Tuesday, a woman died from gunshot wounds when a car she was riding in ignored orders to stop at a police checkpoint in Beirut, officials said. The woman, identified as the wife of the car driver, was shot in the abdomen and died later in the hospital.
The driver, wanted on several warrants, sped off but police gave chase, firing warning shots. He was arrested after abandoning the car and fleeing into a building.
On Monday, troops killed two people and injured a passer-by after a car sped past their checkpoint outside the Beirut international airport. The passer-by died in hospital Tuesday, officials said.
The tensions in Beirut in central Lebanon came as clashes continued in the north. Interior Minister Hassan Sabei, urged the public in a statement to cooperate with security forces "in this critical period."
The soldier's death brings to 31 the number of government troops killed in the fighting since May 20. Most military casualties occurred on the first day, when the army were ambushed on roads or attacked at their posts by the previously little known al Qaeda inspired group.
Twenty civilians and as many as 60 militants have also been reported killed in the fighting at the Nahr el-Bared Palestinian refugee camp on the outskirts of the northern port city of Tripoli.
A weeklong truce at the camp has generally held, but sporadic exchanges of machine gun, rocket and mortar fire continue, including on Tuesday morning.
Hundreds of Lebanese troops have encircled the camp, with the government threatening to storm the area if the militants do not surrender. Fatah Islam has vowed to fight to death.
At the nearby Beddawi refugee camp, where thousands of Palestinians from Nahr el-Bared have taken refuge in recent days, some 200 angry Palestinians staged a demonstration, demanding to return to their homes.
The group burned cardboard boxes, as some shouting "Allahu Akbar," or "God Is Great," tried to march to Nahr el-Bared but were stopped by Lebanese army soldiers at a nearby checkpoint. After a 30-minute standoff, during which traffic on both sides of the street was stopped, the demonstrators dispersed peacefully.
Mediators from major Palestinian factions have been pressing for a negotiated solution. The standoff has raised concerns of more violence across Lebanon, which has a total of 12 highly crowded Palestinian refugee camps where militant movements are rampant.
Also, four bomb blasts have hit the Beirut area since the army-Fatah Islam fighting erupted. One person was killed and about 30 people were injured in the bombings.
Lebanon, particularly Beirut, has been tense after the bombings amid concerns about additional attacks.
On Tuesday, a package placed on the outer wall of a school in the Muslim sector of Beirut raised suspicion and the police were called in, witnesses said. Police bomb experts checked the package, which was said to resemble an explosive charge, but found no explosives inside. Classes were dismissed for the day.