JOHANNESBURG, South Africa -- The Al Qaeda-linked Somali militant group Al Shabab claimed responsibility on Twitter on Saturday for an attack on a Nairobi, Kenya, shopping mall that killed at least 11 people and as many as 30, according to conflicting casualty reports.
Masked gunmen stormed the popular, upscale Westgate mall in Nairobi, the Kenyan capital, at lunchtime Saturday, shooting people and taking others hostage. Police and government officials were swift to call it a terror attack, with witnesses reporting that non-Muslims were targeted.
“The Mujahideen entered #Westgate Mall today at around noon and are still inside the mall, fighting the #Kenyan Kuffar inside their own turf,” Al Shabab’s press office said in one tweet.
"The attack at #WestGateMall just a very tiny fraction of what Muslims in Somalia experience at the hands of Kenyan invaders," it said in another tweet.
The Kenya Red Cross Society, which attended the scene, placed the death toll at around 30 people with 60 injured, while a government official said that 11 deaths had been confirmed. Some witnesses reported even higher casualties.
"We are treating this as a terrorist attack," Police Chief Benson Kibue told reporters.
The Kenyan army and special forces were called in to reinforce police at Westgate mall, which is popular with wealthy Kenyans and expatriates. Military and police helicopters flew overhead as ambulances raced victims to nearby hospitals.
Police tightened security at other shopping malls after the attack.
The United States was gathering intelligence about the attack and had not verified yet that it was conducted by Al Shabab, a U.S. official said.
"There are strong suspicions it was Shabab," the official said. "We are still assessing it."
The CIA and U.S. special operations forces have a small but significant presence in Kenya, one of several staging areas for U.S. intelligence-gathering and counter-terrorism operations in Somalia.
Al Shabab has shown resurgent strength in recent months after being driven from the Somali capital, Mogadishu, in 2011 by a U.S.-backed force from African Union countries.
Al Shabab has sought to strike back at Kenya, which sent troops into southern Somalia in 2011 and pushed the group's fighters out of the port city of Kismayo, once a key source of Al Shabab's revenue. Kenya's troops have struggled to quell the Islamists' control over the countryside.
Al Shabab said in posts on its Twitter account that it had warned there would be consequences when Kenyan forces entered Somalia to fight the militants. The group used the hashtag #Westgate, saying it was a revenge attack.
“By land, air and sea, Kenyan forces invaded our Muslim country, killing hundreds of Muslims in the process and displacing thousands more,” Al Shabab tweeted.
It said it had told the Kenyan government on numerous occastions to withdraw its forces.
“The Kenyan government, however, turned a deaf ear to our repeated warnings and continued to massacre innocent Muslims in Somalia,” Al Shabab said. “For long we have waged war against the Kenyans in our land, now it’s time to shift the battleground and take the war to their land.”
The group’s acounts have been blocked by Twitter several times. The current account has been up and running for a little over a week.
Al Shabab has carried out a number of grenade attacks, shootings and bombings in Nairobi in recent years.
Gun battles with the attackers lasted into the night Saturday. By about 9 p.m., police and special forces had the gunmen surrounded in an area within the shopping complex, Kenyan media reported.
Citizen TV aired footage of victims arriving at a hospital by ambulance, including some who had been shot in the head, people covered in blood and women weeping.
Mutea Iringo, head of Kenya’s Department of Internal Security, said authorities were "taking every measure possible to contain the situation."
“I wish to give reassurance that the government is now fully in charge of the situation and we are confident that the security services will soon bring this matter ... under control,” he said at a news conference. “The government is not taking any chances and had deployed sufficient security services at the scene including specialized units.”
Local media reported gunmen were holding dozens of people hostage.
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 news agency.
Presidential spokesman Manoah Esipisu said the police operation was continuing, with some hostages rescued.
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," 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, the Associated Press reported.
The gunmen targeted non-Muslims and ordered Muslims to leave the mall, according to Elijah Kamau, who was in the mall at the time, Associated Press reported.
"The gunmen told Muslims to stand up and leave. They were safe, and non-Muslims would be targeted," he said.
After the attacks, terrified shoppers trapped in the mall took shelter in shops and a movie theater.
For the record, 3:54 p.m.: An earlier version of this post incorrectly said that Al Shabab was driven from the Somali capital, Mogadishu, in 2012. The correct year is 2011.
Staff writer David S. Cloud in Washington contributed to this report.