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 UN peacekeeping mission said, adding it was still investigating the origin of the blast.

Lebanese Prime Minister Najib Mikati condemned the "targeting" of UN forces in southern Lebanon that wounded three observers.

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.