Three United Nations military observers and their interpreter were wounded Saturday when a shell exploded in southern Lebanon near the border with Israel, a spokesman for the U.N. peacekeeping mission in Lebanon said. 

The observers from Chile, Australia and Norway were in stable condition, spokesman Andrea Tenenti told the Associated Press.

They were part of the United Nations Truce Supervision Organization that supports the U.N. peacekeeping mission in southern Lebanon, Tenenti said.

"Safety and security of UN personnel must be guaranteed. All actors have a responsibility under international humanitarian law to ensure protection to non-combatants, including peacekeepers, journalists, medical personnel, and civilians," Tenenti said in a statement.

"We repeat our call for all actors to cease the current heavy exchanges of fire before more people are unnecessarily hurt," Tenenti continued.

He said the investigation into the explosion is underway. 

The vehicle carrying the three observers and their Lebanese interpreter displayed U.N. markings, Tenenti said. 

The Israeli military and Hezbollah militants have been trading fire across the border between Israel and Lebanon, known as the Blue Line, since the start of the war in Gaza in October, Reuters reported.

The observers were wounded near the border town of Rmeish, Reuters reported, citing security sources.

The Israeli military denied any involvement.

"Contrary to the reports, the IDF did not strike a UNIFIL vehicle in the area of Rmeish this morning," it said in a statement posted on X.