Guerrillas loyal to Palestinian leader Yasser Arafat (search) clashed with militants in Lebanon's largest Palestinian refugee camp Monday. Seven people, including three civilians, were killed, witnesses and Palestinian officials said.

The violence, the worst in a year at the Ein el-Hilweh (search) camp, wounded at least 21 people. Lebanese photographer Mahmoud Zayyat, from the French news agency Agence France-Presse, was slightly injured.

Witnesses and Palestinian officials in the camp said the fighting involved guerrillas of Arafat's Fatah movement and gunmen from the extremist Islamist Al-Nour (search) group, a breakaway faction of the radical Asbat al-Ansar (search) group, which is on the U.S. list of terrorist organizations.

Machine-gun fire and the thud of mortar rounds echoed inside Ein el-Hilweh, located near the southern port city of Sidon (search), the Palestinian officials said on condition of anonymity.

Three Fatah guerrillas were killed in the fighting, witnesses and Palestinian militant group officials said. A militant with Asbat al-Ansar and three civilians were also killed.

On Saturday, a shootout erupted after a guerrilla's funeral near the camp, and Al-Nour's leader, Abdullah Shreidi, was critically wounded. His uncle, Yahya Shreidi, and an unidentified bodyguard were killed. A pro-Arafat guerrilla was killed Friday.

The clashes in recent days are believed to be part of a power struggle between Fatah and militant Palestinian factions.

Abdullah Shreidi has been blamed for several recent bombings in Ein el-Hilweh, the largest of Lebanon's 12 Palestinian refugee camps, with 75,000 refugees.

Rival armed Palestinian groups run Ein el-Hilweh, which is believed to shelter many Islamic militants wanted by Lebanon, including members of Asbat al-Ansar. The Lebanese army mans checkpoints outside the camp, but its troops do not enter.