UNITED NATIONS — As the antigovernment insurgency spread to a second U.N.-run camp in Lebanon yesterday, New York-based U.N. planners said they hoped an armed U.N. force in the southern part of the country could stay out of the fighting.

Two Lebanese Army soldiers were killed yesterday while fighting against militants at the Palestinian Arab camp Ein el-Hilwe in the outskirts of the southern city of Sidon. The fighting involved allies of militants that for two weeks have been battling the Lebanese army in the Nahr el-Bared camp, near the city of Tripoli in the northern part of the country.

U.N. officials say they hoped the fighting in the southern areas could be quickly contained. But they also said that if it spreads, it could soon reach areas near posts of the U.N. Interim Force in Lebanon, where 15,000 mostly European and Asian troops have been deployed since the end of last summer’s Hezbollah war against Israel.

“At the moment, the level of the fighting in Ein el-Hilwe is not very high,” a U.N. official who spoke on condition of anonymity said yesterday. “But 24 hours ago, there was no fighting in Ein el-Hilwe, so this is a very serious juncture.” The official said it would become clearer within the next day or two whether the clashes have been contained, or whether they could spread further.

Washington has aided Lebanon’s army since the May 20 outbreak of the fighting near Tripoli and yesterday President Bush spoke on the phone with an anti-Syrian politician, Saad al-Hariri, who had asked to thank the president personally, according to the national security adviser, Stephen Hadley.

America closely consults with the Lebanese government and may send “some additional items that are already under consideration that we are talking about with the Lebanese forces,” Mr. Hadley said, according to the Associated Press.

Some Lebanese press reports yesterday maintained that UNIFIL-affiliated ships in the Mediterranean have shelled the Nahr al-Bared camp, assisting the Lebanese forces. A U.N. spokeswoman, Marie Okabe, dismissed the reports as “utterly unfounded.”

The closer the fighting gets to the Litani River, the more UNIFIL troops deployed there could get embroiled in skirmishes. Several U.N. sources who spoke on condition of anonymity yesterday said UNIFIL would not get involved in the fighting. But they added that there are three Palestinian Arab camps south of the Litani, including Rashidieh, the largest, where the insurgents may have allies.

The Security Council charged UNIFIL with assisting the Lebanese army, at its request, in creating a weapons-free zone south of the Litani. But yesterday, the Israeli head of the research division of the military intelligence unit, Yossi Baidatz, told a Knesset committee that despite the U.N. presence, Hezbollah is rebuilding its military force with the help of Syria and Iran in defiance of Security Council resolutions.

Hezbollah “is preparing itself for possible conflict in the summer but is not interested in this as it aspires to a period of calm in which to rehabilitate,” Mr. Bidatz said, according to Ha’aretz.

Both Nahr el-Bared, with a population of 30,500, and Ein el-Hilwe, 45,000, were set up by the United Nations for Palestinian Arabs who gained refugee status in 1948. The camps are run by the U.N. Relief and Works Agency, and the Lebanese government has no jurisdiction over them. Even after five generations, residents have no legal status in Lebanon, and the only sources of income are UNIFIL projects and terrorism. While the camps are meant to be weapons-free, various U.N. reports claimed they have become a base of operation for militants, several of them backed by Syria and Iran.