Three United Nations observers and a Lebanese language assistant were injured by a shell that exploded near them while they were patrol outside of Rmeish in southern Lebanon on Saturday.

The Israel Defense Forces (IDF) denied initial reports that it attacked a UN observer vehicle in the area. 

"Contrary to the reports, the IDF did not strike a UNIFIL vehicle in the area of Rmeish this morning," the military said in a post in Hebrew on X, formerly Twitter. Israel's Foreign Ministry later posted the same denial in English.

The United Nations peacekeeping mission in Lebanon, known as UNIFIL, said a shell exploded near the observers as they were carrying out a patrol. They are part of the UN Truce Supervision Organization that supports UNIFIL to monitor hostilities along the demarcation line between Lebanon and Israel, known as the Blue Line.

"The targeting of peacekeepers is unacceptable," UNIFIL spokesperson Andrea Tenenti said.

Norwegian, Australian, Chilean observers injured in incident

One of the observers was a Norwegian citizen, who was lightly injured, the Nordic country's Defense Ministry said. The Lebanese state-run news agency NNA reported the other observers were from Australia and Chile, and the language assistant was from Lebanon. 

According to the reports, they were airlifted in a UNIFIL helicopter. 

Lebanon's caretaker prime minister, Najib Mikati, spoke with UNIFIL commander Aroldo Lozaro, condemning the "targeting" and wounding of UN staff.

The UN's Special Coordinator for Lebanon, Joanna Wronecka, said she was "saddened" to learn of the injuries and that the incident served as "another reminder of the urgent need to return to a cessation of hostilities across the Blue Line."

Since the start of the Israel-Hamas war in Gaza in October, Israel and Lebanon-based Hamas-allied Hezbollah have regularly traded fire across the border.

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

UN's Guterres condemns incident in Lebanon

UN Secretary-General Antonio Guterres condemned the explosion that killed the UN observers, a statement released by his spokesperson said.

"The situation along the Blue Line between Lebanon and Israel since 8 October last year, with daily exchanges of fire between non-state armed groups based in Lebanon and the Israel Defense Forces, continues to be of grave concern," the statement read.

"These hostile actions have not only disrupted the livelihoods of thousands of people, but they also pose a grave threat to the security and stability of Lebanon, Israel, and the region."

UNIFIL is the UN's longest-running observer mission, having started in 1978 in Lebanon to confirm Israeli withdrawal from the country. It currently has 10,000 so-called "Blue Helmets" deployed to Lebanon's southern border region.

Fears of a broader regional conflagration intensified on Friday as Israel struck Hezbollah targets in Syria and Lebanon.

lo/sms (Reuters, dpa, AP)