GARISSA, Kenya, April 2 (UPI) -- The al-Shabab terror group claimed responsibility for an attack on Garissa University College in Kenya resulting in the deaths of at least 147 people Thursday.
Kenyan Interior Minister Joseph Nkaissery said four attackers were killed.
The al-Qaida-linked al-Shabab issued a statement via radio saying it separated Muslim students from non-Muslims in order to conduct an "operation against the infidels."
Witnesses reported at least five masked gunmen stormed the campus, in eastern Kenya, Thursday morning and began firing indiscriminately. The gunmen gained access to the campus and at least two buildings after firing at guards, BBC News reported, killing nearly 150 people. Several students were also taken hostage.
Abdikadir Sugow, spokesman for the Garissa county government, said the attackers were wearing what appeared to be combat gear, including suicide vests or bulletproof vests.
More than 500 students were rescued from the campus. It's unclear how many students were at the school at the time of the attack, but about 900 students are enrolled there.
According to some witnesses, the assailants began firing at worshipers praying inside a campus mosque. In addition to the killed, at least 79 people were injured, Kenya's National Disaster Operation Centre said.
A short time after the attack began, authorities sent troops into the attack zone to track down the gunmen, BBC News reported. Witnesses said the attackers had by that time entered a student residential building and continued firing.
The U.S. Embassy in Nairobi on Thursday called the incident an act of terrorism.
"We are saddened & angered by today's terrorist attack @ #Garissa Univ.," the Embassy tweeted along with the hashtag #CowardsNeverWin.
"29 injured from the Garissa attack have been admitted at Garissa Level 5 Hospital. 4 in critical condition. Majority have gunshot wounds," Kenya's National Disaster Operation Centre tweeted.
The Somali radical group al-Shabab has repeatedly threatened to attack in Kenya. Somalia borders Kenya's eastern flank, where tensions have traditionally run high and retaliatory attacks occur with regularity.
Al-Shabab, a group fully recognized as a terror organization by the United States and Britain, is reportedly attempting to form an Islamic state in Somalia. Garissa is located about 90 miles west of the Somali border.
Earlier this week, British and Australian officials alerted their citizens of potential terrorist activities in various parts of Kenya -- including Garissa.
Earlier this week, the White House announced that President Barack Obama was planning to visit Kenya in July for a business summit. It was not immediately known whether the Garissa attack might impact those plans.