Kenya's foreign minister Amina Mohamed confirmed Monday that two or three of the al-Shabab militants who took over a Nairobi shopping mall, killing at least 62 people, were American citizens.
"From the information we have, they are young men, about 18-19 years old, of Somali or Arab origin," Mohamed told "PBS Newshour.
"That just goes to underline the global nature of the war that we're fighting," she added.
In addition to the Americans, one of the militants was British, she said. The British citizen was a woman who has "done this many times before," Mohamed said.
The Americans lived in "Minnesota and one other place" in the United States, she told PBS.
Earlier tweets from al-Shabab, which claimed responsibility for the attack and is linked to al-Qaida, claimed three Americans were in their ranks. They are from the Minneapolis-St. Paul area of Minnesota and Kansas City, Mo., according to the al-Shabab tweets. Both areas have large Somali-American populations.
State Department spokeswoman Jen Psaki said Monday the department had "no definitive evidence of the nationalities or the identities" of the attackers.
U.S. officials, including the FBI, were looking into the claim that American citizens were involved in the attack. White House spokesman Ben Rhodes said U.S. officials have seen "reports coming out of al-Shabab that indicate information along those lines."
"But we have to run those to ground, of course," he said. "We do monitor very carefully and have for some time been concerned about efforts by al-Shabab to recruit Americans or U.S. persons to come to Somalia.
"This is an issue that has been tracked very closely by the U.S. government, and it's one that we'll be looking into in the days ahead."
There was no answer at the Kenyan Mission at the United Nations on Monday night.
Mohamed said Kenya needs to work with other governments to fight the increasing terrorist threat and "much more with the U.S and the U.K., because both the victims and the perpetrators came from Kenya, the United Kingdom, and the United States. From the information we have, two or three Americans and so far I've heard of one Brit."
Kenyan security forces continued to battle the terrorists in an upscale mall for a third day Monday in what they said was a final push to rescue the last few hostages.
While the government announced Sunday that "most" hostages had been released, a security expert with contacts inside the mall said at least 10 were still being held by a band of attackers described as "a multinational collection from all over the world."
The expert, who insisted on anonymity to talk freely about the situation, said many hostages had been freed or escaped in the previous 24-36 hours, including some who were in hiding.
However, there were at least 30 hostages when the assault by al-Shabab militants began Saturday, he said, and "it's clear" that Kenyan security officials "haven't cleared the building fully."
Flames and dark plumes of smoke rose Monday above the Westgate shopping complex for more than an hour after four large explosions rocked the surrounding neighborhood. The smoke was pouring through a large skylight inside the mall's main department and grocery store, where mattresses and other flammable goods appeared to have been set on fire, a person with knowledge of the rescue operation told The Associated Press.
The explosions were followed by volleys of gunfire as police helicopters and a military jet circled overhead, giving the neighborhood the feel of a war zone.
By evening, Kenyan security officials claimed the upper hand.
"Taken control of all the floors. We're not here to feed the attackers with pastries but to finish and punish them," Police Inspector General David Kimaiyo said on Twitter.
Kenya's Interior Minister Joseph Ole Lenku said the evacuation of hostages had gone "very, very well" and that Kenyan officials were "very certain" that few if any hostages were left in the building.
But with the mall cordoned off and under heavy security, it was impossible to independently verify the assertions. Similar claims of a quick resolution were made by Kenyan officials on Sunday and the siege continued. Authorities have also not provided any details on how many hostages were freed or how many still remain captive.
Three attackers were killed in the fighting Monday, Kenyan authorities said, and more than 10 suspects arrested. Eleven Kenyan soldiers were wounded in the running gun battles.
Al-Shabab said the hostage-takers were well-armed and ready to take on the Kenyan forces.
An al-Shabab spokesman, Sheik Ali Mohamud Rage, said in an audio file posted on a militant website that the attackers had been ordered to "take punitive action against the hostages" if force was used to try to rescue them.
The attackers have plenty of ammunition, the militant group said in a Twitter feed, adding the Kenyan government would be responsible for any loss of hostages' lives.
A Western security official in Nairobi, who insisted on not being named to share information about the rescue operation, said the only reason the siege hadn't yet ended would be because hostages were still inside.
Westgate mall, a vast complex with a casino and multiple banks that have secure vaults and bulletproof glass partitions, is difficult to take, the official said. "They are not made for storming," he said of the labyrinth of shops, restaurants, and offices. "They're made to be unstormable."
Some 12 to 15 al-Shabab militants entered the complex wielding grenades and firing on civilians inside the mall, which includes shops for such retail giants as Nike, Adidas, and Bose, and is popular with foreigners and wealthy Kenyans.
The militants specifically targeted non-Muslims, and at least 18 foreigners were among the dead, including six Britons, as well as citizens of France, Canada, the Netherlands, Australia, Peru, India, Ghana, South Africa, and China. More than 100 people were wounded, including five Americans.
Fighters from an array of nations participated in the assault, according to Kenya Chief of Defense Forces Gen. Julius Karangi. "We have an idea who these people are and they are clearly a multinational collection from all over the world," he said.
Al-Shabab, which means "The Youth" in Arabic, said the mall attack was held in retribution for Kenyan forces' 2011 push into neighboring Somalia.
An extremist Islamic terrorist force that grew out of the anarchy that crippled Somalia after warlords ousted a longtime dictator in 1991, it is estimated to have several thousand fighters, including a few hundred foreign fighters — among them militants from the Middle East with experience in the Iraq and Afghanistan conflicts. Others are young, raw recruits from Somali communities in the United States and Europe.
Somali President Hassan Sheikh Mohamud said the attack showed that al-Shabab was a threat not just to Somalia but to the international community.
If some of the attackers were Somalis who lived in the United States, it illustrates the global nature of the militant group, the Somali leader said in a speech at Ohio State University.
"Today, there are clear evidences that Shabab is not a threat to Somalia and Somali people only," he said. "They are a threat to the continent of Africa and the world at large."
As the crisis passed the 48-hour mark, a video emerged that was taken by someone inside the mall's main department store when the assault began. It showed frightened and confused shoppers crouching as long, loud volleys of gunfire could be heard.
The Associated Press contributed to this report.
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