American citizens were among those killed in the weekend attack on the Intercontinental Hotel in Kabul, US State Department officials told CNN.
The attackers were affiliated with the Pakistan-based Haqqani network, according to the Afghan Interior Ministry. The Taliban released a statement claiming responsibility.
Additional details, including the precise number of Americans killed, were not immediately available.
At least 18 people were killed during a 12-hour standoff with security forces after gunmen raided the hotel, Afghan authorities said.
Of those killed, 14 were foreign nationals and four were Afghans, according to Najib Danish, spokesman for the Ministry of Interior. Four gunmen were also killed by Afghan security forces responding to the attack, he said.
"The attack on the hotel, once again, shows the depravity of terrorists who seek to sow chaos. Sadly, we can confirm that Americans are among the victims," State Department spokesperson Heather Nauert said.
"We express our deepest condolences to our American families and to all the victims of the attack. We are grateful for the bravery displayed by the Afghan National Defense and Security forces. Had it not been for their speedy recovery of the wounded, more lives may have been lost," she added.
The slain included nine people from Ukraine and one person each from Greece, Germany and Kazakhstan, Kabul Police Chief Salem Ehsas said.
US Secretary of State Rex Tillerson issued a statement Sunday condemning the attack.
"The United States stands with the government and people of Afghanistan," he said. "We remain firmly committed to supporting Afghan efforts to achieve peace, security, and prosperity for their country. Violence like what we witnessed yesterday has no place in Afghanistan or anywhere else in the world."
The US State Department had warned last week of a possible attack by extremist groups targeting Kabul hotels.
The Afghan Interior Ministry blamed the Haqqani network for the attack. The group is based in the Pakistani tribal area of Waziristan and known for its high-profile attacks on Western targets in Afghanistan. The network maintains close ties to al Qaeda and the Taliban, and seeks to reestablish Taliban rule in Afghanistan.