Authorities in Kenya found six more bodies on Wednesday evening after the end of a 20-hour siege of a hotel and office complex in Nairobi by a group of Somali militants, taking the toll to 21, CNN reported. Jason Spindler, an American killed by the gunmen, had survived the terror attack on the World Trade Center in New York City on September 11, 2001.

All the five gunmen were killed during the siege. Nine people, including the wife of an attacker, have been arrested so far, according to BBC. Around 28 people were injured in the attack, and all those who were missing have been accounted for.

Somalia-based militant Islamist group al-Shabab has claimed responsibility for the attack. The group said the operation was a response to “the witless remarks of United States President Donald Trump” and his decision to recognise Jerusalem as Israel’s capital, Reuters reported.

Earlier on Wednesday, President Uhuru Kenyatta said 700 civilians were rescued during the siege. “Every person that was involved in the funding, planning and execution of this heinous act” will be relentlessly pursued, he added.

The dead include 16 Kenyans and one person each from the United Kingdom and the United States. The identities of three people of African origin is unclear, said Inspector General of Police Joseph Boinett.

The siege had started around 3 pm (5.30 pm Indian local time) on Tuesday. According to Boinnet, gunmen threw bombs at vehicles in the car park before entering the lobby of the hotel, where one person blew himself up.

Around 8 pm, Interior Cabinet Secretary Fred Matiang’i said, all the buildings in the complex were secured. “The situation is under control and the country is safe,” he said. “Terrorism will never defeat us.”

Al-Shabab, a militant group that opposes the Somali government, carries out attacks throughout East Africa. Kenya is part of a peacekeeping operation that supports the Somali government’s operations against the group.