NAIROBI, Kenya (CNN) -- Fifty-nine dead. At least 175 injured. About 30 hostages still inside, as well as perhaps a dozen gunmen.
Those are the grim numbers, more than a day after Islamist attackers stormed an upscale Nairobi mall on Saturday, spraying bullets and holding shoppers captive.
The tense standoff continued into Sunday night, with sporadic gunfire heard through the day and at least one explosion.
Kenya's President Uhuru Kenyatta told reporters Sunday afternoon the Kenyan people had showed resiliency as a nation and would triumph against the attackers.
The tragedy was also personal; one of his nephews and his fiancee were among the 59 people killed.
"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.
Kenyan government and Western diplomatic sources said Al-Shabaab militants were holding about 30 hostages inside the shopping center.
As grim-faced Kenyan soldiers warily searched the five-story building Sunday -- and as Al-Shabaab maintained its defiant stance -- the siege was no closer to a resolution.
There are 10 to 15 gunmen involved, Kenyatta said.
"We know that they were across the building," State House spokesman Manoah Esipisu told CNN's Zain Verjee. "We know that they are now isolated somewhere within the building."
Soldiers kept vigil outside the mall, guns dangling from their shoulders.
"We want to do everything possible, and the security people are doing everything possible to make sure we lose no more lives," Esipisu said.
More than 175 were injured in the attack, Kenyatta said, offering his support to the wounded and relatives of the dead. He said that 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," he said.
It was the deadliest terror attack in Kenya since al Qaeda blew up the U.S. Embassy there in 1998, killing 213 people.
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.
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.
Late in the day, helicopters approached the mall. Activity around the center picked up briefly but then it was quiet again.
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.
Earlier in the day, 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.
One apparent hostage left the building Sunday, and said she had been hiding in the basement of the mall, CNN affiliate 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 are at the scene and are 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."
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 terrrorism analyst Peter Bergen said it was unlikely.
"It would be very unusual for a woman to be involved in one of these operations," he said. "Typically these groups are misogynist. Their view is the woman should be in a home and shrouded in a body veil."
Lewthwaite's husband, Germaine Lindsey, was one of the suicide bombers killed in the 2005 attack on London's transportation system. His Buckinghamshire-born widow is wanted by Kenyan authorities for her alleged role as an Al-Shabaab and al Qaeda-linked financier.
A day of horror
The calm was shattered around noon local time Saturday. Gunshots erupted as shoppers picked up groceries, savored lunch and browsed through the racks at stores.
Before long, pools of blood smeared pristine hallways. Bodies lay strewn across the floor.
Uche Kaigwa-Okoye was sipping coffee when he heard what first sounded like a fallen table, then the continuing rat-a-tat of gunfire. As the gunshots became louder, screaming crowds headed for the exits.
He joined 20 people who took shelter for about five hours in a women's bathroom cubicle.
"They had grenades, and it was really, really loud," he said of the attackers. He noticed tear gas in the hallways as well.
"All of us felt like they were close," he said.
As people texted family and friends outside the mall, word spread that nobody could be trusted. And even if the good guys could be sorted from the bad guys, the intermittent barrages of gunfire made any escape attempt seem futile.
Sara Head, a Washington resident, experienced similar horror in the mall's parking garage. As her car pulled up, she heard gunfire. She crawled underneath and hid behind cars before getting into a stairwell.
Eventually, the stairwell lights came back on and the door to a nearby supermarket opened. She dashed through, passed a nearby loading dock and fled to safety.
"There was blood throughout the supermarket," Head said. "It wasn't clear if it was OK to exit."
Several Kenyan agencies made a plea for blood donations.
"Hospitals are appealing for more blood, the response is incredible but more is needed," tweeted Francis Kimemia, secretary to the Cabinet.
Foreigners among casualties
Most of the casualties are Kenyan, authorities said. But the mall is popular with expatriates and foreign nationals, who were among those killed and injured.
Those killed include three British citizens, two French nationals and two Canadians, including a diplomat, their governments said.
Several American citizens were among the wounded, including Elaine Dang, a University of California, Berkeley, graduate.
Dang worked as the general manager for Eat Out Kenya, which confirmed her injuries on its Twitter and Facebook pages.
The State Department said Saturday there were several Americans among the injured, but none among the dead. Secretary of State John Kerry didn't offer details.
The U.S. Embassy is asking personnel to stay in place Sunday and avoid the Westgate Mall area and any large gatherings. All U.S. citizens in Kenya are urged to register online so the embassy can provide them with updated information on travel and security -- and can contact them in case of emergency.
Israel's Foreign Ministry said one national was slightly wounded and three escaped. A cafe at the mall is owned by an Israeli, but the ministry does not believe the mall was targeted because of that.
The Ghana president's office said literary figure Kofi Awoonor was among those killed in the attack.
"Such a sad twist of fate to place Prof at the wrong place at the wrong time," President John Mahama said in a statement.