(Adds details of killing, comment from U.N. Somalia chief, background)
MOGADISHU, April 7 (Reuters) - Two foreign consultants working for the United Nations anti-drugs agency in Somalia were shot dead on Monday at an airport in north central Somalia, a U.N. official said.
Aleem Siddique, spokesman for the United Nations Assistance Mission in Somalia (UNSOM), said it was not known who was behind the killing of the two, who were both male. The United Nations will not release their names and nationalities until their families had been notified.
Nicholas Kay, the U.N. Special Representative for Somalia, urged local authorities to investigate what he called the "callous attack" at Galkayo airport.
"The United Nations in Somalia remains committed to continuing our vital support to the Somali people as they emerge from decades of conflict," Kay said in a statement.
The United Nations has spent billions of dollars in Somalia since the outbreak of civil war in 1991 but it has often been targeted by warring clan factions and most recently by Al Qaeda-aligned Islamist group al Shabaab.
Gunmen in the capital used a car bomb to blow a hole in the U.N. compound's wall last June and 22 people, including U.N. staff, were killed in the ensuing firefight.
Al Shabaab in February this year attacked a U.N. convoy with a remote-controlled bomb, killing at least seven Somalis. No U.N. staff were hurt in that attack.
(Reporting by Drazen Jorgic; Editing by James Macharia and Angus MacSwan)