JOHANNESBURG -- At least 11 people were killed Saturday after masked gunmen attacked an upscale shopping mall in Nairobi, the Kenyan capital. The gunmen reportedly took others hostage in what police described as a terrorist attack, with witnesses reporting that non-Muslims were targeted.
The Kenya Red Cross Society placed the death toll at 22, while a government official said that 11 deaths had been confirmed.
Police had the building surrounded Saturday afternoon as military and police helicopters flew overhead, according to Kenyan media reports. The Kenyan army was called in to reinforce police at the Westgate mall, popular with wealthy Kenyans and expatriates.
"We are treating this as a terrorist attack," Police Chief Benson Kibue told reporters.
Reports of casualties varied significantly, with some accounts putting the number of dead higher than 22. About 50 were wounded, according to the Red Cross Society.
Police said the gunmen were holding at least seven people hostage, according to Agence France Presse.
Dozens of traumatized shoppers fled after about five gunmen ran into the mall, threw a grenade and opened fire at lunchtime.
"The casualties are many," Red Cross Society spokesman Abbas Guled told Reuters.
Presidential spokesman Manoah Esipisu said the police operation was continuing, with some hostages rescued.
There was speculation that the attack might be linked to Somali terrorist group Al Shabab, which has carried out grenade attacks, shootings and bombings in Nairobi in recent years, since Kenya sent its army into Somalia against the Al Qaeda-linked militants two years ago.
Gunmen on Saturday targeted non-Muslims and ordered Muslims to leave the mall when the attack started, according to Elijah Kamau, who was in the mall at the time, the Associated Press reported.
"The gunmen told Muslims to stand up and leave. They were safe, and non-Muslims would be targeted," he said.
Kenyan Police Inspector General David Kimaiyo told local media that the rescued hostages were being screened for possible links to the attackers: "We are not taking chances, and rescued hostages are screened," the Nation newspaper reported him as saying.
The gunmen appeared to have entered the mall through a cafe with an outdoor seating area.
"We started by hearing gunshots downstairs and outside. Later we heard them come inside. We took cover. Then we saw two gunmen wearing black turbans. I saw them shoot," said an employee at the cafe, Patricia Kuria, AP reported.
After the attacks, terrified shoppers trapped in the mall took shelter in shops and a movie theater.
No group has claimed responsibility for the attack.