Islamist militants linked to al-Qaida said on Tuesday they were still holding hostages as Kenyan troops battled for a fourth day to end the bloody siege at a Nairobi shopping center.

Sporadic gunfire at the upmarket Westgate mall broke out again at dawn, hours after officials claimed Kenyan troops had wrested back "control" of the sprawling complex from Somalia's al-Shabaab insurgents, who are said to include US citizens and a British woman.

At least 62 shoppers and staff members have been killed and close to 200 wounded in the siege, but concerns are high that the toll may rise, as al-Shabaab is boasting about a "countless number of dead bodies still scattered inside the mall".

The fate of 63 people listed as missing remains unclear.

"The hostages who were being held by the mujahedeen (fighters) inside Westgate are still alive, looking quite disconcerted but, nevertheless, alive," the al-Shabaab said on their latest Twitter post.

In an interview on Monday with US public broadcaster PBS, Kenyan Foreign Minister Amina Mohamed said the attackers included US and British citizens.

"From the information that we have, two or three Americans, and I think so far I have heard of one Brit," she said.

The Briton was a woman, Mohamed said.

"And she has, I think, done this many times before," she told PBS.

"The Americans, from the information we have, are young men, about between maybe 18 and 19," she said, adding they were of Somali or Arab origin but "lived in the US, in Minnesota and one other place.

"So, basically, look, that just was to underline, I think, the global nature of this war that we're fighting," Mohamed added.

However an alleged commander in the Somali al-Shabaab rebel group denied on Monday news reports that Westerners or women were involved in the hostage standoff.

The man, who claimed he had been in contact with the Islamist attackers inside the Westgate shopping center, also said the militants would not negotiate an end to the siege.

The man, who called himself Abu Omar, was speaking to BBC radio after several British newspapers reported that Samantha Lewthwaite, the widow of one of the suicide bombers in the 2005 attacks on the London transport network, could have masterminded the attack.

"There are some rumors spreading around that say that there have been American, British and other attackers of different nationalities involved," Abu Omar said.

"I can confirm to you that none of that is true, I know that is baseless rumors that have no justification for them."

He claimed that women would never be involved in such attacks.

"We do not employ our sisters to carry out military attacks of this type, so these are just baseless rumors that have no substance to them," he said.

The man added, "There will be no negotiations."

Kenyan Interior Minister Joseph Ole Lenku had earlier denied that any of the insurgents were women, although he said some male attackers "had dressed like women".

London refused to be drawn out on Tuesday on Amina Mohamed's comments that a British woman was among the militants behind the mall attack.

A spokesman for the Foreign Office said the ministry was "aware" of Mohamed's comment.

"We continue to liaise very closely with the Kenyan authorities and to support their investigation into this attack," he said.

In 2011 Kenyan police released wanted notices for Lewthwaite, saying she was traveling under a false South African passport with the name Natalie Faye Webb accompanied by her three children, a girl and two boys.

Nairobi's Daily Nation newspaper quoted security sources as saying that extremists on the Kenyan coast call her "Dada Muzungu" - white sister in Swahili - and that she had slipped a Kenyan dragnet in Mombasa in January 2012, when forces raided villas she was believed to have been hiding out in.

AFP-Reuters-Xinhua

A woman reacts at the Nairobi City Mortuary after identifying the body of her father, who was killed in a mall attack in Nairobi. Khalil Senosi / Associated Press

(China Daily 09/25/2013 page12)