Lebanese troops raided an Islamic militant position inside a besieged Palestinian refugee camp, sparking a battle that killed at least four soldiers Friday in renewed fighting in the four-week-old siege of the north Lebanon camp. Troops unleashed artillery barrages into the Nahr el-Bared camp on the outskirts of the northern city of Tripoli on Friday as they stepped up their sustained assault against Fatah Islam, the al-Qaida-inspired militant group barricaded inside. For nearly two hours, troops surrounding the camp pounded with heavy artillery and tank fire suspected militant positions, sending black and gray smoke billowing in the sky, security officials said. The intense bombardment started fires in several shell-punctured buildings in the camp. Early Friday, troops launched a raid into the camp to assault a building where militants were believed to be holed up. In the resulting battle, four soldiers were killed and six others wounded, the officials said, speaking on condition of anonymity because they were not authorized to speak to the media. The officials did not give details on the objective of the raid or say whether it was achieved. While most of the hundreds of Lebanese troops involved in the siege have stayed outside the camp, the military has carried out several such raids inside during the past four weeks of fighting at Nahr el-Bared - trying to take out militant positions without a full-fledged assault. The renewed fighting in the north came a day after anti-Syrian lawmaker Walid Eido, killed in a massive car bombing in Beirut, was buried as tens of thousands of mourners angrily blamed Syria for the killing. In addition to Eido, his son, Khaled, two bodyguards, and six passers-by were also killed in Wednesday's explosion, the latest in a string of bombings to have shaken Lebanon since the fighting erupted in the Nahr el-Bared camp on May 20. Eleven people were also wounded in the blast. Eido was a close friend of former Prime Minister Rafik Hariri, who was similarly assassinated in a Beirut car bombing in 2005. He also was a political ally of Hariri's son, Saad, who now leads the anti-Syrian majority in the Lebanese parliament. Five other anti-Syrian figures have also been assassinated the past two years. Many in Lebanon blame Syria for the killings, but Syria denies any involvement. Eido's assassination was a further blow to the stability of this small Mediterranean nation, which has been mired in a political power struggle between the Western-backed government and the Hezbollah-led opposition, supported by Syria. The fighting between Lebanese troops and Fatah Islam militants has claimed more than 140 lives - 65 soldiers, at least 60 Fatah Islam militants and at least 20 civilians - since its outbreak. The ferocity of combat - the army deploying tanks and field artillery with the militants using mortars, rockets and booby traps - underscored the tough task Lebanon's military was facing in its campaign to destroy militants who have attacked its checkpoints. The army on Friday again accused Fatah Islam militants, who have taken up positions in apartment buildings, basements and even sewers, of using one of the camp's mosques to store arms and fire at troops. The army also says militants have deliberately blown up parts of a mosque to turn public opinion against the military, the state-run National News Agency reported. Fatah Islam leaders have pledged to fight to death rather than surrender. A prominent Palestinian official indicated Thursday that a Palestinian force could be deployed in the camp to end the fighting. "The coming days will bring a solution in which a joint Palestinian force will be deployed in order to stop the bloodshed," Sultan Abuleinein, head of Palestinian President Mahmoud Abbas' Fatah faction in Lebanon, said in remarks carried by the NNA. Most of the camp's 31,000 residents have fled to a nearby camp since the fighting began, but the International Committee of the Red Cross has said that between 3,000 and 6,000 civilians remain behind. The violence at Nahr el-Bared has threatened to spread to the country's 11 other Palestinian refugee camps. Two soldiers were killed in clashes last week with militants in another camp, Ein el-Hilweh, in southern Lebanon.