President Kenyatta on Tuesday announced that a siege of the Westgate shopping mall was over but that the losses were "immense." He said 61 civilians and six members of the security forces were killed in the attack with five gunmen killed and 11 suspects in custody.

The chief prosecutor of the International Criminal Court (ICC) Fatou Bensouda said on Tuesday she was prepared to work with Kenya to prosecute the Islamist al-Shabab fighters who were behind the four-day attack on the Nairobi mall.

The siege has claimed the lives of civilians from numerous countries, including Australia, China and Canada. Some 200 others have been wounded.

The offer from the ICC's Bensouda came after the court in The Hague let Kenyan Deputy President William Ruto fly home to help deal with the crisis. Ruto had been on trial over the violent aftermath of Kenya's 2007 presidential election.

The United Nations envoy for Somalia, Nicholas Kay, on Tuesday called for a redoubling of efforts against al-Shabab. African Union troops stationed in Somalia, mainly around Mogadishu, must be bolstered, Kay said.

"It must be military, but also political and practical... On all three, we need to redouble our efforts," Kay told reporters in Geneva. "The amount of money that we're talking about that's required for the extra effort in Somalia would be very small. But the cost of walking away would be very expensive."

Earlier in the day, an explosion and gunfire was heard from inside the mall at 6.30 a.m. local time (0330 UTC), followed by a minute of sustained gunfire three hours later.

A security expert with contacts inside the mall was quoted by the AP news agency as saying that at least 10 hostages were still be held by the attackers, describing them as a "multinational collection from all over the world."

Earlier, Kenya's Foreign Minister Amina Mohamed had said "two or three Americans" and "one Brit" were among the assailants who had attacked the mall.

The US State Department and the British Foreign Office said they were aware of Amina's count but had no confirmation of identities.

The mall was stormed on Saturday by some 12 to 15 suspected al-Shabab militants who fired on civilians, saying they were targeting specifically non-Muslims. Al-Shabab said the assault was in retribution for a push into Somalia by Kenyan forces in 2011. African Union troops subsequently evicted the rebel group from Mogadishu.

The Nairobi attack is the worst such incident in Kenya since al Qaeda killed more than 200 people when it bombed the US embassy in Nairobi in 1998.

ipj/msh (Reuters, AFP, AP)