Ambushes, attacks and abductions made work for the United Nations more dangerous last year, with the staff union saying 58 colleagues were killed in 2013.

The UN Staff Union says 33 peacekeepers and 25 civilian staffers and contactors were killed last year.

The union says that compares to 37 staffers killed in 2012 and 36 in 2011.

The union also says 16 UN personnel were detained in Syria in 2013, and three remained missing at the end of the year.

The deadliest attack on UN personnel last year was an ambush April 9 by some 200 attackers on 32 peacekeepers escorting a convoy near Gumuruk, South Sudan. It killed five UN peacekeepers, five contractors and two local UN staffers.