Three of alleged attackers at Nairobi mall are from U.S., according to sources within terror group Al-Shabaab. http://t.co/lnKCPMjbUO — CNN Breaking News (@cnnbrk) September 22, 2013

Three of the attackers at the Westgate Mall siege in Nairobi, Kenya, are from the United States, sources within the terror group that orchestrated the attack told CNN on Sunday. CNN reported that the American-linked militants from the terrorist group al-Shabab are among nine people listed on a since-shuttered Twitter account linked to the group. Sources told CNN that other names linked to the account include two individuals from Somalia and one each from Canada, Finland, Kenya and the United Kingdom. They range in age from 20 to 27 years old.Two of the Americans are from Minneapolis-St. Paul, Minnesota, and the other is from Kansas City, Missouri. Minneapolis has a large Somali community that in the past has been linked to recruitment efforts by al-Shabab as well as al-Qaida.The FBI is looking into the claim that American citizens were involved the attack, but have not confirmed that, CNN reported. A senior State Department official told the network that the United States is trying to determine whether any of the alleged attackers are American.At least 68 people were killed in the mall attack by the Somali group, which demanded that Kenya pull troops back from its neighbor Somalia. On Monday, Kenyan officials initially claimed that they had rescued other hostages but were warning that the death toll could rise sharply as troops battled to end the bloody stand-off.

"Our concern is to rescue all hostages alive and that is why the operation is delicate," the Kenya Defence Forces said in its latest update. It did not say how many people were being held by the dozen-or-so attackers.



But by late afternoon, Kenyan troops were involved in a very intense firefight with the terrorists.



Reuters journalists near the upmarket Westgate complex heard sporadic shots and also heavy bursts of rifle fire and muffled blasts on at least two occasions after daybreak. Kenyan troops moved around outside the building. A Kenyan Red Cross official, Abbas Guled, said there had been clashes inside the building.



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But there was no indication of the fate of people whom the authorities had said on Sunday were being held by 10 to 15 gunmen — and possibly women — inside a large supermarket.



The CNN report, which broke on Sunday afternoon, backed up information from Republican Rep. Peter King of New York, a member of the House Intelligence Committee, who warned that al-Shabab has recruited from the United States.



King said the devastating attack showed the growing influence of al-Qaida linked groups in Africa.



"This shows the really growing influence of al-Qaida in Africa. You have al-Shabab now in Somalia going off into Kenya, carrying out an attack outside its own country," King said on ABC's "This Week," before news of the American connection of the attackers became widely known.



The attack showed that "al-Qaida and its affiliates are still extremely powerful and still able to really strike terror into the hearts of people, attacking a shopping mall, it has no military significance at all," King said.



"I would assume that local law enforcement are looking into Somalia-American communities today," King said, adding that US law enforcement will need to ensure a similar attack won't happen on American soil.



U.S. authorities have been looking at the recruiting by al-Shabab in Minneapolis for years, CNN reported, with several prosecutions of recruiters. In recent years, the FBI reports a decrease in recruitment.



The first known American suicide bomber, Shirwa Ahmed, was a Somali American from Minneapolis, Minnesota. Ahmed was among a group who attacked a government compound in October 2008. He drove a car bomb that killed up to 30 people, The New York Times reported in February 2009.



In early September, an American-born member of al-Shabab, Omar Hammami, was reported killed in an ambush ordered by the terror group's leader, with whom he had a falling out. A rapper originally from Alabama, Hammami was favored for his propaganda skills and was known in the organization as Abu Mansoor al-Amriki, or "The American."



What is al-Shabab? It is an extremist Islamic terrorist force that grew out of the anarchy that crippled Somalia after warlords ousted a longtime dictator in 1991. Its name means "The Youth" in Arabic, and it was a splinter youth wing of a weak Islamic Courts Union government created in 2006 to establish a fundamentalist Islamic state in the East African nation.



The group is estimated to have several thousand fighters, including a few hundred foreign fighters. Some of the insurgents' foreign fighters are 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. U.S. officials have expressed fears that militants fleeing Afghanistan and Pakistan could seek refuge in Somalia.



On Sunday, President Barack Obama called Kenyan President Uhuru Kenyatta to offer condolences over what the White House called a "terrorist attack," Reuters reported.

Islamist militants still held hostages on Sunday at the shopping mall, where brief volleys of gunfire interrupted hours of stalemate.

"President Obama called President Kenyatta of Kenya this morning to express condolences to the government and people of Kenya for the terrorist attack carried out by al-Shabab yesterday on the Westgate Shopping Mall in Nairobi," the White House said in a statement. "President Obama reiterated U.S. support for Kenya's efforts to bring the perpetrators of the attack to justice."

Five American citizens were among those injured in the shootings at the mall, said State Department deputy spokeswoman Marie Harf.

There were no reports of any Americans among the dead, said Harf.



Late Sunday Kenyan security forces, aided by Israeli special forces, launched an assault on the upscale Nairobi mall.



The assault, which began shortly before sundown, came as two helicopters circled the mall, with one skimming very close to the roof. A loud explosion rang, far larger than any previous grenade blast or gunfire volley.



Kenyan police said on Twitter that a "MAJOR" assault by security forces had started to end the two-day siege.



"This will end tonight. Our forces will prevail. Kenyans are standing firm against aggression, and we will win," Kenya's Disaster Operations Center said on Twitter.



The assault came about 30 hours after 10 to 15 al-Shabab extremists stormed the mall from two sides, throwing grenades and firing on civilians.



Loud exchanges of gunfire emanated from inside the four-story upscale mall throughout the day Sunday. Kenyan troops were seen carrying in at least two rocket propelled grenades and helicopters hovered over the mall throughout the day. Al-Shabab militants reacted angrily to the helicopters on Twitter and warned that the Kenyan military action was endangering hostages.



Kenyan officials said they would do their utmost to save hostages lives, but no officials could say precisely how many hostages were inside. Kenya's Red Cross said in a statement citing police that 49 people had been reported missing. Officials did not make an explicit link but that number could give an indication of the number of people there were captive.



The death toll on Sunday rose to 68 after nine bodies were recovered in a joint rescue mission.



Somalia's al-Qaida-linked rebel group, al-Shabab, claimed responsibility for the attack that specifically targeted non-Muslims. The attackers included some women. The Islamic extremist rebels said the attack was retribution for Kenyan forces' 2011 push into neighboring Somalia.



Al-Shabab said on its new Twitter feed — after its previous one was shut down on Saturday — that Kenyan officials were asking the hostage-takers to negotiate and offering incentives.



"We'll not negotiate with the Kenyan govt as long as its forces are invading our country, so reap the bitter fruits of your harvest," al-Shabab said in a tweet.



Kenyan President Kenyatta reiterated his government's determination to continue fighting al-Shabab.



"We went as a nation into Somalia to help stabilize the country and most importantly to fight terror that had been unleashed on Kenya and the world," said Kenyatta. "We shall not relent on the war on terror."



He said although this violent attack had succeeded, the Kenyan security forces had "neutralized" many others.



Earlier in the day Kenyatta said his nephew and his nephew's fiance were killed in the attack.



Former Kenyan Prime Minister Raila Odinga told reporters at the mall that a number of people were being held hostage on the third floor and the basement area of the mall, which includes stores for Nike, Adidas and Bose.



Kenyan security officials sought to reassure the families of hostages inside but implied that hostages could be killed. The security operation is "delicate" because Kenyan forces hoped to ensure the hostages are evacuated safely, said Interior Cabinet Secretary Joseph Lenku.



"The priority is to save as many lives as possible," Lenku said, adding that more than 1,000 people escaped the attack inside the mall on Saturday.



"We have received a lot of messages from friendly countries, but for now it remains our operation," Lenku said.



More than 175 people were injured in the attack, Lenku said, including many children. Kenyan forces were by Sunday in control of the mall's security cameras, he said.



Britain's prime minister, in confirming the deaths of three British nationals, told the country to "prepare ourselves for further bad news."



Westgate Mall is at least partially owned by Israelis, and reports circulated that Israeli commandos were on the ground to assist in the response. Four restaurants inside the mall are Israeli-run or owned.



In Israel, a senior defense official said there were no Israeli forces participating in an assault, but the official said it was possible that Israeli advisers were providing assistance. The official, speaking on condition of anonymity because he was discussing a classified military issue, would not elaborate.



Israel has close ties to Kenya going back many years. And in recent years, Israel has identified East Africa as an area of strategic interest and stepped up ties with Kenya and other neighboring countries, due to shared threats posed by al-Qaida and other extremist elements. In 2002, militants bombed an Israeli-owned luxury hotel near Mombasa, killing 13 people, and tried to shoot down an Israeli airliner at the same time.



Kenyans and foreigners were among those confirmed dead, including British, French, Canadians, Indians, a Ghanaian, a South African and a Chinese woman.



Kofi Awoonor, a Ghanaian poet, professor and former ambassador to Brazil, Cuba and the United Nations, died after being injured in the attack, Ghana's presidential office confirmed. Ghana's ministry of information said Awoonor's son was injured and is responding to treatment.



Kenya's presidential office said that one of the attackers was arrested on Saturday and died after suffering from bullet wounds.



Britain's Foreign Office said that Foreign Secretary William Hague has chaired a meeting of Britain's crisis committee and sent a rapid deployment team from London to Nairobi to provide extra consular support.



In a statement, the United Nations Security Council condemned the attacks and "expressed their solidarity with the people and Government of Kenya."



There was some good news on Sunday, as Kenyan media reported that several people in hiding in the mall escaped to safety in the morning, suggesting that not everyone who was inside overnight was being held by al-Shabab.



Cecile Ndwiga said she had been hiding under a car in the basement parking garage.



"I called my husband to ask the soldiers to come and rescue me. Because I couldn't just walk out anyhow. The shootout was all over here — left, right— just gun shots," she said.



Police lobbed multiple rounds of tear gas throughout the day to disperse hundreds of curious Kenyans who gathered near the mall.



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Material from Reuters and the Associated Press was used in this story.

