Secretary-General Ban Ki-moon said four United Nations personnel have been killed in the "horrific attack" on a Kabul restaurant, the Associated Press reports.

A suicide bomber blew himself up outside a Kabul restaurant filled with foreigners and affluent Afghans having dinner Friday, Jan 17 night, while two gunmen sneaked in through the back door and opened fire, kliing 21.

The UN chief condemned the attack "in the strongest terms," saying "such targeted attacks against civilians are completely unacceptable and are in flagrant breach of international humanitarian law," UN deputy spokesman Farhan Haq said.

Ban said the UN personnel, who were not identified, were among at least 14 foreigners and Afghans killed, including a number of people from other international organizations. Kabul police say 16 people were killed. Ban demanded an immediate end to the attacks.

According to BBC News, Wabel Abdallah, the head of the IMF's Afghanistan office, was also killed in the attack. The other victims were Afghans, Canadians, Lebansese and a Briton.

The Taliban claimed responsibility for the attack.