More than 60 people are confirmed dead, and hundreds injured, after the Al-Shabaab fighters overran the premises and took hostages.
Kristina Kukolja has the details.
Kenya's Interior Ministry took to social media to announce security forces had taken control of the Westgate shopping centre.
"We're in control of Westgate, but our forces are combing the mall, floor by floor, looking for anyone left behind," word came from the official Twitter account, adding "We believe all of the hostages have been released."
An operation by Kenyan, Israeli and other foreign troops is said to have now eliminated all resistance from the armed hostage-takers.
Interior Minister Joseph Ole Lenku says government soldiers are committed to seeing out the action to its end.
"Our resolve to defend our country has never been higher, and we want to say that we will take the war to the criminals' doorsteps. This is our country. We are in control of the security situation. Kenyans should take comfort that the country is in our hands."
Speaking in New York ahead of the annual United Nations General Assembly meeting, President Barack Obama said his country is ready to extend an offer of law-enforcement support to Kenyan authorities.
"I've had the opportunity to speak to President Kenyatta about the terrible tragedy that happened in Nairobi and we are providing all the cooperation that we can as we deal with this situation that has captivated the world. I want to express personally my condolences, not only to President Kenyatta, who lost some family members in the attack, but to the Kenyan people. We stand with them against this terrible outrage that has occurred."
Australia's Foreign Minister, Julie Bishop, has added her voice to the international wave of condemnation and condolences over the Nairobi shopping centre deaths.
Ms Bishop, also in New York for the annual UN gathering, says events in the Kenyan capital are a reminder that terrorism remains a threat to the world community.
"A tragic reminder that terrorism remains a global threat, one Australian is among those killed and I extend my sympathies to nations who have lost citizens and to families who have lost loved ones."
It's expected that the Nairobi killings will be the subject of debate at the UN meetings.
And in The Hague, Vice-president William Ruto has been given leave from his war crimes trial at the International Criminal Court to return to Kenya.
Speaking to Al Jazeera, Kenya's Foreign Minister Amina Mohamed said the incident has become a matter of international relevance.
"You had Canadians, you had British, you had Americans who died in there, Ghanaians, Africans from other parts of the continent, some Asians. So it's something that has touched everybody across the world. So, it's not even a truly Kenyan affair anymore. Yes, we provided the venue, I guess. But it has touched everybody, and both the victims and the perpetrators came from across the world."
In Australia, Tasmania's Premier Lara Giddings has tabled a condolence motion in Parliament to honour architect Ross Langdon and his Netherlands-born partner, Elif Yavuz, who were killed in Nairobi.
Both she and Tasmanian opposition leader Will Hodgman took the opportunity to express their sympathies.
"This house, one, expresses great sadness at hte death of Mr Ross Langdon, his wife Elif Yavuz and their unborn child in the recent terrorist attack in Nairobi, Kenya." // "Can I say on behalf of the opposition that we fully support the first motion moved by the Premier this morning and would extend our condolences."
Feature by Kristina Kukolja
