A sonic hand grenade was tossed into a field late Friday east of the southern port city of Tyre, 80 kilometres south of Beirut, Lebanese police said, according to dpa. The sound of the bomb caused panic in the area and prompted police and ambulances to rush to the area of Housh, the police said. The bomb blast came a day after an explosion rocked an industrial area north of Beirut, killing one person and wounding five others. Lebanon since May 20 has been rocked by five explosions, which have so far killed two people and wounded dozens of others. The explosions came after violent clashes that pitted the Lebanese army and an Islamist militant group called Fatah al-Islam since May 20 in northern Lebanon. In the meantime, Lebanese troops continued to pound late Friday al-Qaeda-inspired militants dug in at a Palestinian refugee camp in northern Lebanon after the group rejected demands to surrender. The heavy thud of machinegun fire echoed across the area as fires raged inside and clouds of smoke billowed over the camp, abandoned by most of its 40,000 residents. Witnesses said at least 30 civilians were evacuated by relief workers. "Army units are ... gradually taking control of the terrorists' positions with the aim of ending this abnormal situation that was imposed on Lebanon," an army statement said, adding the militants had no choice but to face justice. Friday's fierce fighting resumed after two days of mostly sporadic clashes and came hours after negotiations carried out by Palestian and Lebanese Islamist clergymen failed to convince Fatah al-Islam militants to surrender. The militants, who have vowed to fight to their death, have repeatedly rejected demands by Lebanese authorities to give up their weapons or to surrender. dpa wh gma