The United Nations raised Monday serious concerns over reports suggesting Israel used U.S.-supplied white phosphorus munitions in southern Lebanon.

U.N. spokesperson Stephane Dujarric told Anadolu Agency (AA) that they did not have any information to confirm, but were "obviously very concerned about any use of these types of incendiary munitions, especially in populated areas."

The Washington Post reported on the Oct. 16 Israeli attack in Dheira, a Lebanese town near the border with Israel, in which at least nine civilians were wounded.

Human rights group Amnesty International has called for an investigation, labeling the incident a potential war crime.

Among the nine injured in the attack, at least three were hospitalized, one for days, according to the report.

Anadolu has also taken some photographs showing the use of white phosphorus bombs on civilians in Gaza, while several lawyers said they can be used as evidence in a complaint against Israel.

The White House, in the meanwhile, also expressed concerns over the reports, adding that it was seeking more details about the allegations.

Lebanon had accused Israel of repeatedly using the incendiary weapon in October, while the Washington Post on Monday said analysis of shell fragments from one attack showed the rounds were U.S.-made.

"We've seen the reports, we're certainly concerned about that. We'll be asking questions to try to learn a little bit more," said National Security Council spokesperson John Kirby.

The use of white phosphorus as a chemical weapon is prohibited under international law, but it is allowed for illuminating battlefields and can be used as a smokescreen.

"Obviously, any time that we provide items like white phosphorus to another military, it is with the full expectation that it will be used in keeping with those legitimate purposes and in keeping with the law of armed conflict," said Kirby.

A journalist working for the newspaper found remnants of three artillery rounds with serial numbers showing they were made in the United States in 1989 and 1992, it said.

Lebanon said on Oct. 31 that Israel's use of the weapon in "repeated" attacks – amid tensions following the Oct. 7 Hamas incursion – had burned 40,000 olive trees.

The United States has strongly backed Israel but has been trying to keep the conflict from spreading throughout the region, especially to Lebanon where the Iran-backed Hezbollah group is based.

Kirby said it was "also in the context of that, that we're concerned about these reports" on the use of white phosphorus.

State Department spokesperson Matthew Miller added that the United States was "looking for additional information."

"Anytime that we saw white phosphorus being used in a way that would harm civilians, of course, it's something that we would be concerned about," Miller added.