Kenyan police say there is still “an active security operation” Wednesday in and around the luxury hotel and shopping complex attacked by Islamic extremist gunmen.

Sporadic gunfire could be heard from the scene in the morning after scores of people were rescued at daybreak as police continued what they called a mopping-up exercise.

At least 15 people were Killed in the attack which started Tuesday by car bombs followed by at least four armed men who invaded the Hotel and shops.

Al-Shabaab — the Somalia-based extremist group that is allied to al-Qaida — claimed responsibility for the carnage at the DusitD2 hotel complex, which includes bars, restaurants, offices and banks and is in Nairobi’s well-to-do Westlands neighborhood with many American, European and Indian expatriates.

Al-Shabaab carried out the 2013 attack at the nearby Westgate Mall in Nairobi that killed 67 people.

Kenyan President Uhuru Kenyatta is expected to address the nation Wednesday morning and the Kenyan Red Cross is to make a statement about Tuesday’s attack.

A Kenyan police officer said 15 bodies had been taken to the morgue. He spoke on condition of anonymity because he was not authorized to speak to reporters.

The U.S. State Department confirmed that an American citizen was among those killed, but did not release the victim’s identity. Al-Shabaab asserted that 47 people were killed but its Shahada news agency post gave no details.

Authorities sent special forces into the hotel to flush out the gunmen. Early Wednesday, Kenya’s Interior Ministry said in a tweet that all buildings had been secured and there was no further threat to the public.

Hours later, at dawn, another explosion and gunfire were heard. The Interior Ministry said authorities were “mopping up” the scene but did not give details on the fate of the attackers.

“To God be the Glory. We have been rescued. Over 50 people in my group. No injuries Thank you all for the support and prayers. Thanks You KDF,” tweeted a Kenyan businesswoman, Aggie Asiimwe Konde. KDF stands for the Kenya Defense Forces.

Lucy Wanjiru said she had been trying to flee when she saw a woman on the ground floor get shot. Wanjiru ended up in a washroom with several other scared people. Her friend Cynthia Kibe stayed in contact with her by phone overnight.

“I think I panicked when she told me that the gunshots are next to her,” Kibe said. “I had to keep telling her ‘Just wait, help is on the way, they are almost there, they are almost there.’

And then at one point she was like, ‘Please tell me I am getting out of here alive’ and then it was just like my breaking point.”

Authorities did not say how many attackers there were — or what happened to them — though Kenya’s Citizen TV aired security-camera footage that showed at least four heavily armed men in dark-colored, paramilitary-style gear.

The coordinated assault began with an explosion that targeted three vehicles outside a bank, and a suicide bombing in the hotel lobby that severely wounded a number of guests, said Kenya’s national police chief, Joseph Boinnet.

Kenyan hospitals appealed for blood donations even as the number of wounded remained unclear.

Associated Press video from inside the hotel showed Kenyan security officers searching the building and scared workers emerging from hiding while gunfire could still be heard. Some climbed out a window by ladder. One man got up from the floor where he appeared to be trying to hide under a piece of wood paneling, then showed his ID.

Like the attack at the Westgate Mall, this one appeared aimed at wealthy Kenyans and foreigners. It came a day after a magistrate ruled that three men must stand trial in connection with the Westgate Mall siege.

Al-Shabaab has vowed retribution against Kenya for sending troops to Somalia to fight it since 2011. Tuesday’s violence came three years to the day after al-Shabaab extremists attacked a Kenyan military base in Somalia, killing scores of people.

The al-Qaeda-linked group has killed hundreds of people in Kenya. In the deadliest attack, al-Shabaab claimed responsibility for an assault on Kenya’s Garissa University in 2015 that killed 147 people, mostly students.

The latest carnage demonstrated al-Shabaab’s continued ability to carry out spectacular acts of bloodshed despite a dramatic increase in U.S. airstrikes against it.