NAHR AL-BARED, Lebanon (Reuters) – Lebanese troops and al Qaeda-inspired militants fought sporadically at a refugee camp in north Lebanon on Wednesday and a Palestinian force took up positions to defuse tension at another camp in the south.

Soldiers fired artillery and tank shells at the coastal Nahr al-Bared camp overnight as the army tightened its grip around Fatah al-Islam militants holed up inside.

At least 114 people, including 46 soldiers, have been killed in the fighting since it erupted on May 20. The army says the militants started the conflict and demands their surrender.

The battles are Lebanon’s deadliest internal conflict since the 1975-1990 civil war.

In south Lebanon, a 40-member force made up of Palestinian President Mahmoud Abbas’s Fatah group and three Islamist factions deployed at the northern entrance of Ain al-Hilweh camp, scene of deadly clashes this week between the army and the militant Jund al-Sham group, which has links to Fatah al-Islam.

The Ain al-Hilweh fighting, in which two soldiers and two militants died, raised concerns that the conflict in the north could spill over to refugee camps elsewhere in the country.

Palestinian factions, including Fatah and the Islamist Hamas group, oppose Fatah al-Islam, which shares al Qaeda’s ideology of global jihad and recruits fighters from other Arab countries.

About 27,000 of Nahr al-Bared’s 40,000 refugees have fled, many of them to the nearby Beddawi camp. UNRWA, the U.N. agency that cares for Palestinian refugees, has launched an appeal for $12.7 million to meet the urgent needs of the displaced.

The Beirut government said the United States, which sent ammunition and other equipment to the army after the conflict started, had donated $3 million towards helping the displaced.

A 1969 agreement prevents the army from entering Lebanon’s 12 camps, home to about half its 400,000 Palestinian refugees.

The violence is the latest jolt to stability in Lebanon. Four bombs have exploded in the Beirut area, killing one person and wounding dozens, since the Nahr al-Bared fighting began.

A small bomb was found near a beach resort popular with U.N. peacekeepers in south Lebanon on Wednesday morning, security sources said. They said the 2 kg (4.4 pound) charge had been timed to go off at 6 a.m. (0300 GMT) but it failed to detonate.

Fatah al-Islam last week accused the 13,000-strong U.N. force, which has a naval component, of shelling Nahr al-Bared from the sea, a charge denied by the peacekeepers.