BEIRUT - Three United Nations observers and a translator were wounded on Saturday when a shell exploded near them as they were carrying out a foot patrol in south Lebanon, the U.N. peacekeeping mission said, adding it was still investigating the origin of the blast.

UNIFIL said in a statement the targeting of peacekeepers is "unacceptable".
Two security sources had earlier told Reuters the observers were wounded in an Israeli strike.

The Israeli military denied involvement in the incident. "Contrary to the reports, the IDF did not strike a UNIFIL vehicle in the area of Rmeish this morning," the military said in a statement.

The security sources said the incident occurred outside the border town of Rmeish. One of the security sources said the car carried three U.N. technical observers and one Lebanese translator.

The mayor of Rmeish, Milad Alam, told Reuters that he had spoken with the translator and confirmed his condition was stable.

"From Rmeish, we heard a blast and then saw a UNIFIL car zipping by. The foreign observers were taken to hospitals in Tyre and Beirut by helicopter and car," Milad said, without providing details on their condition.

Israel has been trading fire with the Lebanese armed group Hezbollah in southern Lebanon for nearly six months in parallel with the war in Gaza.

Israel's shelling of Lebanon has killed nearly 270 Hezbollah fighters, but has also killed around 50 civilians - including children, medics and journalists - and hit both UNIFIL and the Lebanese army.

The U.N. technical observer mission, which is unarmed and known as UNTSO, monitors the demarcation line between Lebanon and Israel. UNIFIL is an armed peacekeeping mission.