Three floors of the Westgate mall have collapsed in the final stages of its hostage siege, burying an unknown number of people, including several of the attackers, Kenyan President Uhuru Kenyatta has disclosed in a televised speech to the nation.
"The operation is now over," he said. "As I had vowed earlier, we have ashamed and defeated our attackers."
Mr. Kenyatta did not explain how the three floors of the mall collapsed, although explosions have been audible in the mall for several days and a huge fire has been burning since Monday.
Nor did he explain the fate of the hostages, believed to number at least 30 at the beginning of the siege. It was unclear whether some of the hostages may be buried in the rubble.
The death toll so far includes 61 civilians, six security officers, and five attackers who were shot dead, along with "several" others who were trapped in the rubble of the mall collapse, Mr. Kenyatta said in the speech on Tuesday.
But the toll is expected to rise sharply in the days to come as bodies are recovered.
A Twitter account purporting to speak for the attackers blamed Kenyan authorities for the deaths, accusing Kenyan troops of firing chemical agents into the mall and then demolishing part of it in an attempt to bury bodies and evidence.
Mr. Kenyatta announced three days of national mourning for the victims of the prolonged four-day Westgate siege, which appeared to be largely finished on Tuesday, although security forces were still combing the building for explosives and bodies.
Mr. Kenyatta said 11 suspects were in custody, but this appeared to include 10 people who were detained and questioned at Nairobi's international airport as they attempted to leave the country. Their role in the Westgate attack, if any, is unclear.
There are a total of 240 dead and injured from the mall siege so far, Mr. Kenyatta said, apparently including 175 people whose injuries were already reported. But the Kenyan Red Cross has registered more than 50 missing people, and local morgues are preparing to receive up to 60 additional bodies, in addition to those already listed as dead, news agencies say.
About 10 to 15 attackers, believed to be from the Somalia-based Islamist radical militia al-Shabab, stormed into the mall on Saturday with guns blazing, shooting dozens of people. The attackers were a "multinational" group, Kenyan officials say.
In his speech, Mr. Kenyatta acknowledged that some of the attackers may have been U.S. or British citizens, but he said forensic experts are still gathering evidence.
His Foreign Minister, Amina Mohamed, had earlier told a U.S. television network that the attackers included "two or three" Americans and a British woman. She hinted that the woman may have been the notorious "white widow" – British citizen Samantha Lewthwaite, 29-year-old widow of London subway suicide bomber Jermaine Lindsay, who is believed to have entered Kenya on a false South African passport. But there is no firm evidence of her involvement, and al-Shabab has denied that any women were involved in the attack.
Most of Mr. Kenyatta's speech to the nation was a fervent defence of Kenya's handling of the crisis. "Kenya has stared down evil and triumphed," he said. "As a nation, our head is bloodied, but unbowed. The criminals found us unafraid, as we ever shall be. We cannot be conquered."
Kenya has defeated "the monster of terrorism," he said. "These cowards will meet justice, as will their accomplices and patrons, wherever they are."
He did not discuss, however, any plans for boosting security to prevent a repeat of the siege. In parliamentary debates on Tuesday, many MPs complained about security lapses and failures by Kenya's police and intelligence agencies. One MP said the international community was more aware of security threats in Nairobi than the national authorities. Others complained of corruption and incompetence among the police and immigration authorities.
Kenyan authorities have been insisting since Sunday that the hostage siege was almost over. They said that their soldiers are in full control of the Westgate mall and are merely "mopping up" and checking for explosives. But its claims were repeatedly contradicted by evidence of persistent fighting, including a huge blaze at the mall that was still burning on Tuesday afternoon, 24 hours after it began. For much of the day, gunfire and explosions continued to erupt.
Meanwhile, the prosecutor of the International Criminal Court, Fatou Bensouda, said on Tuesday that she is ready to work with Kenyan and international authorities to ensure that the Westgate attackers are "brought to justice."
Kenya's parliament has voted to withdraw from the international court in the wake of the court's decision to put Kenya's president and deputy president on trial for alleged crimes against humanity. But the ICC is eager to show that it will not ignore Kenyan injustices, despite the parliamentary vote.
In a separate decision, the court refused to postpone Mr. Kenyatta's trial. He had sought to delay the trial until January, but the court ruled that the trial should go ahead as scheduled on Nov. 12.