The U.S. State Department said Friday it is investigating whether Israel may have used cluster munitions in Lebanon in violation of agreements with the United States restricting their use. A United Nations agency said earlier this week it has found abundant evidence that Israel used the bombs against Hezbollah guerrillas, some in populated areas of southern Lebanon.

The Bush administration defended Israel's overall military campaign against Hezbollah as an act of national self defense. But officials here acknowledge that an inquiry is under way as to whether the Israelis used U.S.-supplied cluster munitions in civilian areas in violation of unpublished agreements with Washington.

The New York Times first reported the investigation Friday. It said a bureau of the State Department was conducting the probe after hearing reports that three types of American cluster munitions - anti-personnel weapons that spread tiny "bomblets" over a wide area - were found in southern Lebanon and had caused civilian casualties.

The newspaper said agreements governing Israel's use of U.S. cluster bombs date back to the 1970s when they were first supplied, and are understood to require that they be used only against organized armies in conventional war situations.

In a talk with reporters, State Department acting spokesman Gonzalo Gallegos would provide few details of the U.S. inquiry but acknowledged that officials have received reports that the weapons might have been misused and are looking into them. "We were provided information from NGOs on the ground. We take it seriously, of course. We're looking into it see the veracity of the claims. And we'll make determinations based on the evidence that we're able to find," he said.

An official who spoke to reporters here on terms of anonymity would give no time-frame for concluding the investigation but said it was being conducted on an expedited basis.

The New York Times account said the charges against Israel are not unprecedented and that that Reagan administration imposed a six-year ban on sales of cluster weapons to Israel in the 1980s, after a congressional inquiry found that they had been used improperly in Israel's 1982 Lebanon invasion.

There have also been a number of U.S. inquiries over the years, all of them apparently inconclusive, into charges of Israeli violations of the 1976 Arms Export Control Act, which requires that American-supplied weapons be used in legitimate self defense.

The United Nations Mine Action Coordination Center said in a report earlier this week that it had found hundreds of unexploded bomblets of American origin in scores of locations in southern Lebanon since hostilities between Israel and Hezbollah guerrillas ended earlier this month.

A spokesman for the Israeli embassy in Washington said Israel has not been informed of the U.S. investigation, but when and if it is, it would happily respond.

The Israeli military has said it sought to avoid civilian casualties in its drive into Lebanon and that it used all weapons in conformance with international law. Israel officials say that by contrast Hezbollah indiscriminately fired hundreds of rockets into Israeli towns during the 34-day conflict with no other intent but to harm civilians.