Militant group, Al-Shabab, stormed a university in northeastern Kenya at dawn on Thursday April 2, killing scores of people in the sect's bloodiest attack in the country, officials said.

CNN reports that the attack left about 147 people dead and dozens injured.

The terrorists took hostages during a 15-hour siege until they were killed by security forces. Christians and converts to Islam appeared to have been the targets.

More than 550 students were evacuated in the standoff on the Garissa University campus located about 90 miles from the Somali border, government officials said. The Somali-based Islamic terrorist group al-Shabab claimed responsibility for the attack — the al-Qaeda-linked organization's deadliest in Kenya.

Students said the gunmen separated Christians from Muslims and held hostages in a dormitory, Kenya's National Police Service said. Explosives were reportedly staged around the Christian hostages. School officials said students reported the gunmen attended morning prayers at the campus mosque before heading to the dorm.

Kenyan Interior Cabinet Secretary Joseph Nkaissery said some students were also killed during morning prayers at the mosque.

A student at the university, Jackson Kamau, said the militants killed those who were likely converts to Islam. Locals can differentiate between Somali Muslims born into Islam and those who have converted because they come from different ethnic groups.

"We'll not allow terrorists to divide our country on religious lines," majority leader in Kenya's 

National Assembly, Aden Duale, said.

Most of the 147 dead were students, but the two security guards, one policeman and one soldier also were killed in the attack, Nkaissery said.

Heavy gunfire erupted at the college as the Kenyan military worked to end the siege. Police Inspector General Joseph Boinett said a dusk-to-dawn curfew will be in place in Garissa and three neighboring counties starting Tuesday, April 7 through April 16.

The White House strongly condemned the attack and said the United States was providing assistance to the Kenyan government.

"We extend our deep condolences to the families and loved ones of all those killed in this heinous attack, which reportedly included the targeting of Christian students," White House spokesman Josh Earnest said in a statement.

Kenyan police are offering a $220,000 bounty for Mohammed Mohamud, also known as Dulyadin and Gamadhere, who they believe is the mastermind of the attack.

Al-Shabab has carried out several attacks in Garissa and across Kenya in the past few years, including the 2013 attack at the Westgate shopping mall in Nairobi that left 67 people dead, and others on mosques in Mombasa, a coastal city in the east.