Al-Qaeda-inspired Fatah al-Islam militants holed up in the northern Lebanon Palestinian refugee camp of Nahr al-Bared killed four Lebanese soldiers in intense fighting Thursday, according to dpa. A high ranking-Lebanese security source said: "Two soldiers were killed in the early hours of the morning and two others fell martyrs during the day." The source said some of the soldiers were killed by sniper fire and others while dismantling booby traps left behind by the militants. The four deaths raised to 129 the number of troops killed since the fighting began on May 20. Fierce fighting erupted on Thursday as troops pounded the remaining Fatah al-Islam hideouts in the old sector of the camp with artillery and tank fire, the state-run National News Agency reported. Three army helicopters flew over Nahr el-Bared, apparently searching for militants, but made no bombing runs, it added. According to Palestinian sources, 12 militants were killed since Wednesday by the Lebanese army. In response to the army's shelling, Fatah al-Islam militants fired six Katyusha rockets on villages near the camp, causing damage to a power plant but no casualties. The rockets were fired from the seafront area in Nahr al-Bared and hit the Deir Ammar power station causing minor damage, Ahmed Eid, the head of the municipality at Deir Ammar, said. Eid said one of the rockets landed near one of the reservoirs, causing a fire that was quickly contained. Another rocket hit a building, while three others landed on the grounds of the facility. The power station was shut down after the rocket attack. Kamal Hayek, chairman of the state-owned electricity company, told Lebanon's official news agency that production at the 400 megawatt facility was halted while damage was assessed. Most of the 40,000 residents have fled the camp in the meantime. Remaining are around 60 women and children - most of them family members of Fatah al-Islam militants. The army has refused to halt its military offensive before the militants fully surrender, but the gunmen have vowed to fight to the death. In Beirut, military experts defused a Katyusha rocket wired to a timer and set to explode, security sources said. The device was found near the Palestinian refugee camp of Sabra on Beirut's outskirts. The conflict in Nahr el-Bared is Lebanon's worst internal violence since the 1975-90 civil war.