In south Lebanon, a 40-member force made up of the Fatah group pf Mahmoud Abbas, the Palestinian president, and three Palestinian Islamist factions deployed at the northern entrance of Ain al-Hilweh refugee camp.
"The Palestinian refugees are not being treated properly by Lebanon"
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Ain al-Hilweh was scene of deadly clashes this week between the army and the Jund al-Sham group, which has links to Fatah al-Islam.
The south Lebanon fighting, in which two soldiers and two fighters died, raised concerns that the conflict in the north could spill over to refugee camps elsewhere in the country.
Palestinian factions, including Fatah and Hamas, oppose Fatah al-Islam, which shares al-Qaeda's ideology and recruits fighters from other Arab countries.
At the Nahr el-Bared refugee camp, more Fatah Islam fighters reportedly surrendered to a major Palestinian faction.
Major General Khaled Aref, a senior Fatah commander at Ain el-Hilweh refugee camp, said on Lebanese television that a total of about 20 Fatah Islam fighters had surrendered to his group in the southern part of Nahr el-Bared.
The surrenders, if true, were the first time a major Palestinian group responded to calls by Lebanese authorities to campaign against Fatah al-Islam.
Palestinian factions have been trying to mediate an end to the battle.
The government wants the fighters to surrender, but Fatah al-Islam leaders have vowed to fight to death.
In another development, Lebanese police said, two Syrians and an Iraqi had been detained near the Syrian border on Wednesday for possessing arms and explosives.
The arrests were made in the village of Bar Elias in the Bekaa valley of eastern Lebanon, about 10km from the main border crossing to Syria, the police said.
Police found weapons, explosives, detailed maps of villages and cities and night-vision goggles in their hideout.
Elsewhere, a small bomb was found near a beach resort popular with UN peacekeepers in south Lebanon.
Security sources said the 2kg charge had been timed to go off at 6am local time (0300 GMT) on Wednesday but it failed to detonate.
Fatah al-Islam last week accused the 13,000-strong UN force, which has a naval component, of shelling the Nahr al-Bared refugee camp from the sea, a charge denied by the peacekeepers.