Authorities in Kenya appeared close to ending a deadly siege Monday at an upscale Nairobi mall, where attackers have killed at least 68 people, injured 175, and are believed to still be holding about 10 people hostage.
"All efforts are underway to bring this matter to a speedy conclusion," the Kenyan military announced on Twitter.
It said that "most of the hostages have been rescued and security forces have taken control of most parts of the building."
Earlier, police had tweeted that a "MAJOR assault" by security forces was ongoing.
The developments come some two days after Al-Shabaab militants first stormed the shopping center, spraying bullets and unleashing chaos.
There are believed to be between 10-15 gunmen involved in the attack, officials said.
Sources within Al-Shabaab told CNN that nine names listed on a Twitter site -- now suspended -- were people who were among the alleged hostage-takers.
Three of the alleged attackers are from the United States, two are from Somalia and there is one each from Canada, Finland, Kenya and the United Kingdom, according to the list.
The FBI is looking into the claim that American citizens were involved the attack, but have not confirmed that.
Similarly, a senior State Department official said that the United States is trying to determine whether any of the alleged attackers are American. But, the official said, authorities are becoming more confident American citizens were involved.
Kenyan President Uhuru Kenyatta vowed Sunday to hold those responsible for the violence, accountable.
The tragedy is personal for the president; one of his nephews and his fiancee were among the dead.
"They shall not get away with their despicable, beastly acts. Like the cowardly perpetrators now cornered in the building, we will punish the masterminds swiftly and indeed very painfully," Kenyatta said.
'Bunch of cowards'
Sporadic gunfire could be heard throughout the day Sunday, and at least one explosion. Those sounds were followed by periods of tense silence.
Soldiers kept vigil outside the mall, guns dangling from their shoulders. Later in the day, helicopters approached.
The Kenyan Red Cross tweeted that nine bodies were recovered Sunday night, bringing the death toll to 68.
More than 175 were injured in the attack, Kenyatta said. He and other Kenyan officials visited hospitals Sunday morning.
"No one should lose their life so needlessly, so senselessly and no family should have to receive news that their loved ones have been killed by a criminal bunch of cowards," the president said.
The mall siege was the deadliest terror attack in Kenya since al Qaeda blew up the U.S. Embassy there in 1998, killing 213 people.
Al-Shabaab, al Qaeda's proxy in Somalia, claimed responsibility, and said it was not backing down. In a message on its Twitter feed, the group said "all Muslims" were escorted from the mall before the attack.
"When justice is denied, it must be enforced," it said in a tweet Sunday. "Kenyans were relatively safe in their cities before they invaded us & killed Muslims #Westgate"
Since Kenya launched attacks against Al-Shabaab in Somalia in 2011, the group has hurled grenades at Kenyan churches, bus stops and other public places.
Last year, the Kenyan military played a major role in handing Al-Shabaab forces a defeat when as part of a peacekeeping mission, they liberated the key Somali port of Kismayo.
The attack Saturday targeted a popular weekend meeting spot. Kenyans and expatriates gather at the luxurious Westgate Shopping Mall on weekends to drink lattes, catch a movie or browse through the more than 80 stores.
Police in Kenya grew irritated as people took to social media to describe what they were seeing and hearing.
"If you must Facebook or tweet, then talk about football or your favourite music but NOT MISINFORM the public on security operations!" authorities said on Twitter.
Three injured security forces were taken out of the besieged mall, but the severity of their injuries was unclear.
By Sunday afternoon, at least 1,000 people had been freed from the mall, Kenyatta said. But some 30 people were believed to still be held.
Later, that number fell to no more than 10, military spokesman Cyrus Oguna told CNN affiliate KTN.
"The number that is still left in the building is very, very small," he said, without providing details on how people got out.
One apparent hostage left the building Sunday, and said she had been hiding in the basement of the mall, KTN reported.
Al-Shabaab vowed not to negotiate with Kenyan authorities.
"The Mujahideen are still strong inside #Westgate Mall and still holding their ground," the group tweeted late Saturday.
Israeli special forces were at the scene and were working with their Kenyan counterparts in the hostage crisis, Kenyan government sources told CNN.
Kenyatta said several nations had offered help but "this remains an operation of the Kenya security agencies."
State House spokesman Manoah Esipisu said there were reports of a white woman among the hostage takers. Kenyan intelligence officials were investigating the claims, he said.
Esipisu was asked if the reported woman was thought to be the infamous Al-Shabaab-affiliated "White Widow," Samantha Lewthwaite. "Nothing is being ruled out," he said.
But CNN terrorism analyst Peter Bergen said it was unlikely.