Kenya mall attack: About 30 hostages still inside

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, a day after attackers stormed an upscale Nairobi mall, spraying bullets and holding shoppers captive.

Kenya's President Uhuru Kenyatta told reporters Sunday afternoon the tragedy was personal; one of his nephews and his fiancee were among the 59 people killed.

"We will punish the masterminds (of the attack) 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.

By noon Sunday, as grim-faced Kenyan soldiers warily searched the five-story building -- and as Al-Shabaab maintained its defiant stance -- the siege was no closer to a resolution.

Officials believe 10 to 15 gunmen are involved, State House spokesman Manoah Esipisu said Sunday.

"We know that they were across the building," Esipisu told CNN's Zain Verjee. "We know that they are now isolated somewhere within the building."

More than 175 were injured in the attack, Kenyatta said.

It was the deadliest terror attack in the nation since al Qaeda blew up the U.S. Embassy in 1998, killing more than 200 people.

The attack Saturday targeted a popular weekend meeting spot. Kenyans and expatriates gather at the luxurious Westgate 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"

As the sun rose Sunday, the standoff between Kenyan forces and the attackers continued.

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.