Five United Nations employees have been abducted by unknown armed men in southern Yemen while returning to Aden after a field mission.

The staff were abducted on Friday in the Abyan governorate, according to 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 on Saturday.

UN Spokesman Stephane Dujarric declined to answer questions on the matter at a press conference, saying “we are aware of this case but, for obvious reasons, we are not commenting”.

An official at the UN office in Aden told Reuters news agency and the Associated Press that four of those abducted were Yemeni nationals.

Yemen’s internationally recognised government, which is based in south Yemen, told state media on Saturday it was working to safely free the workers with the UN Department of Security.

The secessionist Southern Transitional Council, which controls much of Yemen’s south and is at odds with the Yemeni government, condemned the abductions as a “terrorist operation”, according to AP.

Abductions are frequent in Yemen, where armed tribesmen and al-Qaeda-linked armed fighters take hostages to swap for prisoners or cash.

Yemen has been mired in violence since the Iran-aligned Houthi movement overthrew 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 factions, al-Qaeda and the ISIL (ISIS) armed group have, in the past, carried out attacks including in the south, which last year saw protests over deteriorating economic conditions.

The war in Yemen has killed tens of thousands of people and caused a dire humanitarian crisis, with 80 percent of Yemen’s population reliant on aid. (Al Jazeera and News Agencies)

Update news