A pro-government army soldier carries Yemen’s national flag as he walks at the strategic Fardhat Nahm military camp, around 60 kilometers from Sanaa, Feb. 11, 2016. Photo: Reuters / Ali Owidha / File.

Five United Nations staff have been abducted in southern Yemen while returning to Aden after a field mission, the United Nations said on Saturday.

The staff were abducted on Friday in Abyan governorate, said Russell Geekie, a spokesman for the top UN official in Yemen.

“The United Nations is in close contact with the authorities to secure their release,” Geekie said.

Yemen’s internationally recognized government, which is based in south Yemen, was working to safely free the UN staff abducted by unknown gunmen, the official news agency on Saturday cited a cabinet statement as saying.

An official at the UN office in Aden told Reuters that four of those seized were Yemeni nationals.

Yemen has been mired in violence since the Iran-aligned Houthi movement ousted the government from the capital, Sanaa, in late 2014, prompting a military coalition led by Saudi Arabia to intervene months later.

Among Yemen’s many destabilizing forces are Islamist militant groups Al Qaeda and Islamic State that have in the past carried out attacks, including in the south, which last year saw protests over deteriorating economic conditions.

The war has killed tens of thousands of people and caused a dire humanitarian crisis, with 80% of Yemen’s population reliant on aid.