The United States and Nigeria have condemned in the “strongest terms” an attack Thursday by Islamist militants who massacred nearly 150 students at a university in Kenya.

“The US condemns in the strongest terms today’s terrorist attack against the innocent men and women of Garissa University College in Kenya,” a White House statement said.

Nigeria’s outgoing President Goodluck Jonathan described the killings as “heinous” and “barbaric”.

A statement from Jonathan’s office said the president “utterly condemns the deliberate targeting of innocent persons, schools and other soft targets by terrorists.”

“Such atrocious, despicable and barbaric acts of violence ought to have no place in any civilised society,” it said.

Masked gunmen, hurling grenades and firing automatic rifles, stormed the university in the northeastern town of Garissa as students were sleeping.

Officials said at least 147 students were killed in the attack, which was claimed by Somalia’s Shebab Islamistic group and lasted 13 hours.

It was the worst attack in Kenya since the 1998 bombing of the US embassy in Nairobi by Al-Qaeda, when 213 people were killed by a huge truck bomb.

“The United States is providing assistance to the Kenyan government, and we will continue to partner with them as well as with others in the region to take on the terrorist group al-Shebab,” White House press secretary Josh Earnest said.

“The United States stands with the people of Kenya, who will not be intimidated by such cowardly attacks,” he said in a statement.