Updated at 4:50 p.m. ET
Kenya's National Disaster Operation Center says the government's operation against al-Shabab militants on a university campus in Garissa is over. It says that 147 people were killed, along with four militants.
The center added that 587 students had been evacuated from the building; 79 people were injured. It said all students were accounted for. The school reportedly is attended by more than 800 students.
The attack reportedly started with explosions and the killing of two guards, as gunmen attacked around 5:30 a.m., local time. The attackers then entered a dormitory. Al-Shabab, an Islamist group from neighboring Somalia, says it released Muslims after separating them from Christians, some of whom were killed.
From Nairobi, NPR's Gregory Warner says it's the deadliest attack on Kenyan soil since the bombing of the U.S. Embassy in 1998.
"The gunmen had chosen a block of university dorm rooms ideal for a standoff, with a clear line of sight in all directions. ... The attack which began at dawn didn't end until after nightfall, when security forces fired on the gunmen, detonating their explosive vests."
Gregory said there have been frequent attacks in Garissa, a highly militarized town that is 100 miles from the porous Somali border, but none where so many civilians were targeted at once for so long.
Thursday's attack comes two years after the siege by al-Shabab on Westgate Mall in Nairobi. That attack killed nearly 70 people. The group says it's punishing Kenya for supplying troops to fight Islamist extremists in Somalia.
Garissa University College got its start in the 1990s as a teacher teaching college, according to its website. The school was upgraded in 2011; it says it is now "the first and only public institution of higher learning offering approved university degree courses in the region."