Security operations are continuing in Nairobi, where al-Shabab rebels have seized an upmarket mall following an attack which left 39 people dead.
An unknown number of hostages are still being held by Islamist gunmen who are locked in a stand-off with security forces inside Nairobi's Westgate shopping mall, the Kenyan government said early Sunday.
"Hostage numbers still unknown, but they are in several locations. No communication as yet.
Upper levels (of the mall) have been secured," the government's National Disaster Operation Centre said in a situation update posted on Twitter.
An AFP correspondent at the scene said operations by security forces were continuing, 17 hours after the attack began and as dawn approached in the Kenyan capital.
Somalia's Al Qaeda-linked Shabab rebels have claimed responsibility for the attack, which Kenyan President Uhuru Kenyatta said had left 39 dead and 150 more wounded.
"The work is continuing, but you cannot rush these things," an army officer posted on the perimeter cordon said.
"Our teams are there, we are watching and monitoring, we will finish this as soon as we can."
Both the UN Security Council and the United States have condemned the attack.
"The members of the Security Council condemn in the strongest possible terms today's terrorist attack in Nairobi, which has caused numerous deaths and injuries," the council said in a unanimous declaration also extending condolences to the victims and their families.
The 15 council member states also reiterated their condemnation of terror in all its forms and vowed to "combat all forms of terrorism."
"The members of the Security Council expressed their solidarity with the people and Government of Kenya at this difficult time," the statement added.
US Secretary of State John Kerry called the attack "a heartbreaking reminder that there exists unspeakable evil in our world which can destroy life in a senseless instant."
"Attacks like this can't change who we are, a people committed to peace and justice for all, but rather must reaffirm our determination to counter extremism and promote tolerance everywhere," Kerr said in a statement.
"As we prepare to bring the world's leaders together at the United Nations next week, we are reminded again in tragedy of our common humanity."
In a statement from the White House, a spokesperson for the National Security Council said the US would help bring the perpetrators of the attack to justice.
"We will continue to stand with the Kenyan people in their efforts to confront terrorism in all its forms, including the threat posed by al-Shabaab," said NSC spokeperson, Caitlin Hayden.
"This cowardly act against innocent civilians will not shake our resolve."
Four American citizens were reported injured in the Saturday attack on a shopping mall in Kenya. The wife of a foreign service national working for the US Agency for International Development was killed, US officials said.
Al-Shabab Twitter account suspended
The Twitter account of Somalia's Al Qaeda-linked Shabab rebels was suspended Saturday after they used the site to claim responsibility for the attack on a Nairobi shopping mall .
A message from Twitter on the English-language @HSM_Press account read that the account was suspended.
It’s the third time this year that the group has been expelled from the site.
According to Twitter, users are blocked "for any unlawful purposes or in furtherance of illegal activities".
Al- Shabab's previous account, @HSMPress, was suspended in January after the group posted photographs of a French commando they killed and threatened to execute Kenyan hostages.
They opened another account, @HSMPress1, but were again suspended earlier this month after threatening Somalia's internationally-backed president.
The group issued a string of messages on Twitter Saturday, claiming its fighters were behind an attack on Nairobi's upmarket Westgate shopping mall.
"The Mujahideen entered #Westgate Mall today at around noon and are still inside the mall, fighting the #Kenyan Kuffar (infidels) inside their own turf," the Islamist militants had said on Twitter.
"What Kenyans are witnessing at #Westgate is retributive justice for crimes committed by their military," the group said. –Sapa-AFP