The United Nations Secretary-General Ban Ki-moon condemned an attack by Islamist gunmen on a Nairobi mall on Sunday, confirming a former UN employee was among the dead.

“I condemn in the strongest terms yesterday’s terrorist attack at Nairobi’s Westgate Mall.

This premeditated act targeting defenceless civilians is totally reprehensible. The perpetrators must be brought to justice as soon as possible. Scores have been killed and wounded.

I express my condolences to the families of the deceased and injured and the loved ones of all those of other nationalities that are the victims.

Nairobi is the United Nations main headquarters in Africa with a wide ranging presence and hundreds of national and international staff. I’m saddened to report that retired staff of UNICEF was among those killed in the attack,” he said.

Islamist militants were holed up with hostages on Sunday at the shopping mall, where at least 59 people have been killed in an attack by the al Shabaab group that opposes Kenya’s participation in a peacekeeping mission in neighbouring Somalia.

A volley of gunfire lasting about 30 seconds interrupted a stalemate of several hours,an area that has Israeli-owned outlets and is frequented by expatriates and Kenyans.

Foreigners, including three Britons and two diplomats – one from Canada and another from Ghana – were killed in Saturday’s attack at the upmarket mall, claimed by Somali group al Shabaab,an information the British Prime Minister, David Cameron has confirmed also and reacted to.

Shortly after the shots were fired, troops in camouflage ran crouching below a restaurant terrace along the front of the building that had been buzzing with customers when assailants charged in. One witness said they first told Muslims to leave.

For hours after the brazen attack, the dead were strewn around tables of unfinished meals. At one burger restaurant, a man and woman lay in a final embrace after they had been killed, before their bodies were removed. Pop music was left playing.

The assault was the biggest single attack in Kenya since al Qaeda’s East Africa cell bombed the U.S. Embassy in Nairobi in 1998, killing more than 200 people. In 2002, the same militant cell attacked an Israeli-owned hotel on the coast and tried to shoot down an Israeli jet in a coordinated strike.