The terrorist attack began at midday Saturday, Nairobi time, with an estimated 10 to 15 gunmen taking over the mall in what hospital volunteer Abiti Shah said witnesses told her was "like a Hollywood action scene."
"They just started firing in the air," Shah said, retelling the witness accounts.
A youth cooking competition was taking place at the mall at the time, and terrified shoppers fled for their lives as gunfire echoed through the building.
Witnesses said the gunmen went from store to store, shooting people, and then took hostages.
Survivor Bendita Malakia, a North Carolina woman who moved to Nairobi in July, told CNN affiliate WAVY that she took refuge behind the closed metal gates of a store with dozens of others.
"While we were back there, you could hear them methodically going from store to store, talking to people and asking questions," she said. "They were shooting, screaming. Then it would stop for a while and they would go to another store."
Al-Shabaab has claimed that the attackers targeted non-Muslims and vowed they would not negotiate for the hostages' lives. CNN security analyst Peter Bergen said the terrorists apparently took hostages only to prolong the siege and win more media attention.
Most of the dead were said to be Kenyans.
Six British citizens, two French nationals, two Indians and two Canadians, including a diplomat, also died, their governments said.
Those killed include:
• Elif Yavuz, a senior vaccines researcher for the Clinton Health Access Initiative based in Tanzania. Yavuz, a Dutch national, was pregnant and expecting her first child in October, according to Julio Frenk, dean of faculty at the Harvard School of Public Health. "Elif was brilliant, dedicated, and deeply admired by her colleagues, who will miss her terribly," the Clinton family said in a statement. The Dutch Foreign Affairs Ministry confirmed a 33-year-old Dutch woman had been killed.
• A major African poet, author and Ghanian statesman, Kofi Awoonor, Ghana's president said. Awoonor received his Ph.D. from New York's Stony Brook University and was a professor of literature there in the 1970s.
• The nephew of Kenyan President Uhuru Kenyatta and the man's fiancee.
• A Peruvian doctor, Juan Jesus Ortiz, who had previously worked for the United Nations Fund for Children and lived in Kenya doing consulting work, the country's Foreign Affairs Ministry said.
• Sridhar Natarajan, 40, an Indian national and employee of a local pharmaceutical firm, and 8-year-old Paramshu Jain, the son of a bank branch manager, CNN sister network CNN-IBN reported, citing government officials in New Delhi.
Kenyatta said more than 175 people had been wounded. Five were Americans, the State Department said Sunday.
Elaine Dang, 26, a University of California, Berkeley, graduate from San Diego, underwent surgery to her chest, arms and legs.
"I'm OK, I'm very grateful to be alive," she told CNN affiliate KFMB-TV
She said two friends died in the attack.
The Somalia-based Al-Shabaab terror group had said on Twitter that it had sent the gunmen to the mall in retaliation for Kenya's involvement in an African Union military effort against the group, which is al Qaeda's proxy in Somalia.
Last year, the Kenyan military was part of a peacekeeping force that defeated Al-Shabaab forces to liberate the key Somali port of Kismayo.
Since Kenya launched attacks against Al-Shabaab in Somalia in 2011, the group has hurled grenades at Kenyan churches, bus stops and other public places.