An Irish soldier was shot and killed on a U.N. peacekeeping mission in Lebanon and a second was in a critical condition after a hostile crowd surrounded their armoured vehicle, Ireland’s defence minister said on Thursday.

The soldiers, part of the United Nations Interim Forces in Lebanon (UNIFIL), were on what Simon Coveney, who is also Ireland’s foreign minister, said was considered a standard run from UNIFIL’s area of operations in south Lebanon to Beirut when the incident happened in Al-Aqbieh late Wednesday.

“The two armoured vehicles effectively got separated. One of them got surrounded by a hostile mob, I think that’s the only way you could describe them, and shots were fired. Unfortunately, one of our peacekeepers was killed,” Coveney told Irish national broadcaster RTE.

“This was not expected. Yes there has been some tension on the ground between Hezbollah forces and UNIFIL in recent months but nothing like this,” Coveney said.

Hezbollah is a powerful armed group and a heavyweight political party with significant support in the country’s south.

UNIFIL has operated in Lebanon since 1978 to maintain peace along its border with Israel to the south. It was expanded after a U.N. resolution that halted the 2006 Israel-Hezbollah war in southern Lebanon.

Senior Hezbollah official Wafiq Safa told Reuters on Thursday that the soldier’s death came after an “unintentional incident that took place between the residents of Al-Aqbieh and individuals from the Irish unit.”

He asked that the party not be “inserted” into an incident it had no part in, adding that residents had been hit by UNIFIL cars in the crash.

Safa said he had spoken to the force’s head, Aroldo Lazaro, to express the party’s condolences.

UNIFIL said it was coordinating with the Lebanese army and had launched an investigation but details remained “sparse and conflicting.”

The U.N.’s special coordinator for Lebanon, Joanna Wronecka, said on Twitter: “A quick & thorough investigation to determine the facts of this tragic incident is crucial.”

Lebanon’s caretaker premier, Najib Mikati, urged all parties to “show wisdom and patience.” The Lebanese army offered its condolences but did not give additional details.

The United States on Thursday condemned “in the strongest terms the violent attack on UNIFIL peacekeepers,” and said generally that hostility against peacekeepers “is unconscionable.”

‘SHOCKED’

In Al-Aqbieh on Thursday, Reuters saw a UNIFIL vehicle crashed into a shop and flipped onto its side. The army had cordoned off the area.

The convoy carrying eight personnel was travelling to Beirut as two of the members were returning to Ireland on compassionate leave following the death of family members, Irish defence forces chief of staff Seán Clancy told RTE.

The second soldier remains in a U.N.-managed hospital after having undergone surgery, Clancy said.

The two other soldiers in the vehicle were being treated for minor injuries while the four personnel from the other vehicle were not injured.

Coveney, in New York for a U.N. Security Council meeting, said he will meet U.N. Secretary General António Guterres later on Thursday to discuss the incident.

Irish peacekeepers have been in Lebanon since 1978 and it is the first Irish fatality there in two decades, Coveney said.

“We’re all very shocked and deeply saddened, it is a reminder to us of the extraordinary sacrifices that our peacekeepers make on a constant basis,” Irish Prime Minister Micheál Martin told reporters in Brussels.