One soldier was killed and three were wounded in clashes Thursday between the army and Islamic militants in a Palestinian refugee camp in northern Lebanon, while a raid on a suspected militant hideout in the country's east uncovered three vehicles rigged with explosives.

The fighting with the Fatah Islam militants in the northern Nahr el-Bared camp, which erupted May 20, as well as this week's clashes at the Ein el-Hilweh camp near the southern city of Sidon, along with several recent bombings in and around Beirut, have raised fears that Lebanon is heading for more violence.

Security officials, speaking on customary condition of anonymity, said the army's fatality Thursday was gunned down by Fatah Islam snipers in Nahr el-Bared. Earlier in the day, the Al Qaeda-inspired militants attacked an armored personnel carrier, wounding three soldiers, two of them seriously.

The army retaliated with artillery, tanks and heavy machine gunfire at suspected Fatah Islam positions.

Three explosives-rigged vehicles, two cars and a van, were discovered near the town of Bar Elias in eastern Lebanon's Bekaa Valley, hidden in a garage, along with several rockets, the officials said. Witnesses saw at least one blindfolded suspect taken away by the troops.

The raid came a day after three foreign militants — two Syrians and an Iraqi — were captured nearby. It was not immediately known if the militants were Fatah Islam, but several suspected group members have been seized or killed in the region in the past three weeks.

Since May 20, over 100 people, including 46 soldiers and some 60 Fatah Islam militants, have been reported killed in what has been the worst internal violence since the 1975-90 civil war ended. Also, at least 20 civilians have been reported killed in Nahr el-Bared, where thousands of Palestinians remain trapped. Recent civilian casualties are unknown.

The United States and Arab allies have been rushing military supplies to Lebanese army to help strengthen it ahead of a possible full-out assault on the militants barricaded in Nahr el-Bared.

The U.S. airlift, however, has drawn criticism from Hezbollah, the U.S.-backed government's top domestic opponent, whose leader warned Lebanon was being dragged into a U.S. war against al-Qaida that would destabilize the country.

On Thursday, U.S. Defense Department spokesman Bryan Whitman said the United States had completed 21 airlift missions to provide ammunition to Lebanon, and that the airport team that unloaded the planes landing in Beirut had left.

In the northern region of Koura, Lebanese troops surrounded a local university after a loud boom shook the campus Thursday. The school later said the sound was caused by exploding fire crackers. A stun bomb went off late Wednesday in Beirut's Christian suburb of Furn al-Shubak, and another was reported in the mountain's overlooking Beirut.

Since fighting broke out, four explosions in Beirut and in nearby areas have killed at least one person and wounded 40 others.

Also Thursday, judicial authorities charged three Fatah Islam suspects with membership in a "terrorist organization." Thirty Fatah Islam suspects are currently in custody.

Lebanon is home to 400,000 Palestinians, most of whom oppose groups such as Fatah Islam. However, impoverished and densely packed Palestinian camps have become fertile ground for groups such as Fatah Islam.

The Palestinian Liberation Organization's representative in Lebanon, Abbas Zaki, said Thursday that Lebanon's Palestinians should be allowed to set up their own security force inside the camps to prevent formation of armed gangs in the future.

Speaking after talks with Palestinian President Mahmoud Abbas in the West Bank town of Ramallah, Zaki said the PLO proposes a force of 4,000 to 5,000 members for the Lebanon camps.