Fresh gunfire and explosions have been heard at a shopping mall in Kenya's capital, Nairobi.
At least 69 people have been killed and more than 170 have been injured since September 21 in fighting between militants and security forces at the Westgate mall.
Reports say up to 15 militants and an unknown number of hostages are still inside the shopping center. Somalia's Al-Qaeda-linked Al-Shabab movement has said it was behind the attack.
The Kenyan Army said it had secured most of the luxury mall, which is partly Israeli-owned.
The attackers stormed the sprawling four-story complex on September 21, using machine guns and grenades.
A senior Kenyan police official, General David Kimaiyo, said on September 23 that security forces had rescued more hostages overnight.
Kimaiyo, in a Twitter feed, said that "very few" hostages were remaining inside the mall as special forces were "closing in on the attackers." He did not specify the exact number of hostages.
The Red Cross said at least 63 people were recorded missing, thought to include hostages as well as those possibly killed or still hiding in the 48-hour-long siege.
Kenyan President Uhuru Kenyatta vowed in an address to the nation on September 22 that the attackers will be punished "swiftly, and indeed very painfully."
"The Al-Shabab terror group have claimed responsibility for this cowardly act of terror on social media," he said.
"However, investigations are under way to conclusively establish those responsible for this mayhem, so that we can have full accountability. They shall not get away with their despicable and beastly acts."
Al-Shabab has said the operation was in response to Kenya's military involvement in Somalia.
Some 4,000 Kenyan troops are inside southern Somalia, where they have been fighting Islamist militants since 2011.
British Prime Minister David Cameron, meanwhile, is due to hold a meeting with his government's emergency response committee on the siege.
Three British nationals have been confirmed among those killed. It is not known whether there are more Britons among the hostages.
"It is an absolutely sickening and despicable attack of appalling brutality," Cameron said on September 22. "What we know is that three British nationals have been killed. Because the situation is ongoing, we should prepare ourselves for further bad news."
Meanwhile, the International Criminal Court announced on September 23 it was allowing Kenya's Vice President William Ruto -- who is on trial on charges relating to postelection violence in 2007 -- to return to Nairobi for a week to help deal with the crisis.
With reporting by Reuters and AP