An attack on a luxury hotel in Nairobi killed 14 civilians Tuesday, including one American, before security forces subdued the gunmen.

Kenyan authorities declared that the violence had ended multiple times, only to be contradicted by bursts of gunfire that kept police busy for several more hours. Al-Shabab, the Islamic extremist group based in Somalia, claimed responsibility for the attack, carried out by at least four armed men.

“All the terrorists have been eliminated,” President Uhuru Kenyatta said in a televised address Wednesday morning. We are grieving as a country and my heart and that of every Kenyan goes out to the innocent men and women violated by the senseless violence. … We will seek out every person that was involved in the funding, planning and execution of this heinous act.” Kenyatta said rescue teams had evacuated more than 700 people, according to the Associated Press.

The series of apparently coordinated attacks rocked a hotel complex in Kenya’s capital on Tuesday, when an explosion tore through a bank in the compound at about 3 p.m. local time. Then a suicide bomb detonated in the lobby of the nearby DusitD2 hotel, before attackers entered the hotel, shooting.

The U.S. State Department confirms that an American was killed, but has not released his or her name. Cabinet Secretary for Interior Fred Matiang’i had said in a statement Tuesday night that the hotel complex had been secured. However, bursts of gunfire were still heard in the area, NPR’s Eyder Peralta reported from Nairobi.

“Even as the sun rose over Nairobi, the Kenyan military was still trading fire with suspected terrorists in the hotel compound,” Peralta reported. “Through the night and into the morning, dozens of people were rescued from the hotel. Many of them were rushed to hospitals with serious injuries.”

Al-Shabab, the Islamic extremist group that claimed responsibility for the attack, is the same group that attacked the Westgate Mall in Nairobi in 2013, where 67 people were killed.

“Authorities say one of the gunmen blew himself up at the hotel restaurant,” Peralta said. “The other gunmen then moved through the hotel complex, and eventually some of them barricaded themselves in one of the top floors.” Kenyan officials described the operation as a mopping-up exercise, the AP reported.

Similar to the Westgate siege, the attacks on Tuesday appeared aimed at Nairobi’s wealthy residents, including foreigners. Visitors to the upscale hotel, which is located in a leafy area of the Westlands neighborhood, have to pass through two security checkpoints and an airport-style scanner.

It’s not clear how the attackers managed to infiltrate the complex.