West on the Kenya case

US, British and Israeli agencies are helping Kenya investigate the attack by Islamist militants on a Nairobi shopping mall that killed at least 72 people and destroyed part of the complex.

After a four-day siege, President Uhuru Kenyatta said on Tuesday troops had defeated the al-Qaeda-linked al-Shabab group that targeted the shopping centre. He declared three days of mourning.

The attack has highlighted the reach of the Somali al-Shabab and the capabilities of its crack unit, confirming international fears that as long as Somalia remains in turmoil it will be a recruiting and training ground for militant Islam.

The militants stormed the upmarket Westgate Mall in a hail of gunfire and grenades at lunchtime on Saturday. The attack ended on Tuesday when troops detonated explosives to get through locked doors inside the mall as they searched for militants and booby traps.

"We have moved to the next phase," Interior Minister Joseph ole Lenku told a news conference yesterday. Alongside US, UK and Israeli agencies, Kenya was receiving help from Germany, Canada and Interpol in the investigation.

Ole Lenku said he did not expect the death toll of 61 civilians, six members of the security forces and five attackers to rise significantly. The only bodies still likely to be found were those of assailants.

Three floors collapsed after the blasts and a separate fire weakened the structure of the vaulted, marble-tiled shopping mall. Officials said the blaze arose from militants lighting mattresses as a decoy.

Ole Lenku said the investigation would seek to ascertain if there were females among the attackers, as some witness accounts suggest.

Al-Shabab has denied any women took part. It said it launched the attack to demand that Kenya withdraw its troops fighting with African peacekeepers in Somalia.

It said hostages were killed when Kenyan troops used gas to clear the mall. Officials dismissed this as "propaganda".

Kenyatta has said Kenyan forces would not leave Somalia.

"We have shamed and defeated our attackers," he said on Tuesday.

US President Barack Obama said he believed Kenya would continue to be a regional pillar of stability.

Eleven people suspected of involvement in the raid are in custody, but officials have not said how many, if any, were gunmen taken alive and how many were people arrested elsewhere.