In a televised address on Tuesday night, President Uhuru Kenyatta confirmed the end of a standoff between Kenyan security forces and Islamist al-Shabab fighters at a mall in Nairobi.

"We have shamed and defeated our attackers. That part of our task is completed," President Kenyatta said. "Our losses are immense," Kenyatta added.

The president announced Kenya would honor the memories of the "innocent, harmless victims" with three days of mourning, startíng on Wednesday.

Dozens of people - including Australian, Chinese and Canadian citizens - plus an additional six soldiers lost their lives in the siege, which began on Saturday. The Kenyan president said five attackers had been shot dead and eleven suspects had been taken into custody.

The figures are difficult to verify. On Wednesday Somalia's Shabab insurgents claimed via Twitter that 137 hostages had been killed, which would me more than people officially registered as missing.

Roughly 15 suspected al-Shabab militants stormed the mall on Saturday and firing on civilians, saying they were targeting specifically non-Muslims. The assault was in retribution for a push by Kenyan forces into Somalia in 2011 which resulted in their removal from the region, the Somalia-based extremist group said.

The Kenyan president praised his countrymen for their courage in the face of the country's worst terrorist incident in over a decade and for showing warmth and generosity toward the victims and victims' families.

"Fellow Kenyans, we have been badly hurt…but we have been brave, united and strong. Kenya has stared down evil and triumphed…we have not been shaken," he said, adding, "Our country is safe."

Siege draws international concern

The al-Shabab attack in Nairobi drew international attention and condemnation. On Tuesday, the chief prosecutor of the International Criminal Court (ICC) Fatou Bensouda indicated she was prepared to work with Kenya to prosecute the suspects behind the assault.

The United Nations envoy for Somalia, Nicholas Kay, also called for redoubling of efforts against al-Shabab on Tuesday, saying that African Union troops stationed in Somalia must be bolstered.

"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."

World powers have condemned the deadly attack, the deadliest in Kenya since 1998 when al-Qaeda bombed the US embassy in Nairobi, killing 200 people.

kms,hc /rg(AP, AFP, Reuters, dpa)