Rescue workers walk near a Nairobi-bound bus that was ambushed outside Mandera town, near Kenya's border with Somalia and Ethi­o­pia Saturday. Passengers were reportedly pulled from a bus, then gunned down by Islamist militants. (Stringer/Reuters)

Somalia’s Islamist extremist rebels, al-Shabab, attacked a bus in northern Kenya at dawn Saturday, singling out and killing 28 passengers who could not recite an Islamic creed and were assumed to be non-
Muslims, Kenyan authorities said.

Nineteen men and nine women were killed in the bus attack, said Kenyan police chief David Kimaiyo. Al-Shabab claimed responsibility for the killings through its radio station in Somalia, saying it was in retaliation for raids by Kenyan security forces carried out last week on four mosques on the Kenyan coast.

Kenya’s military said it responded to the killings with airstrikes later Saturday that destroyed the attackers’ camp in Somalia and killed 45 rebels.

“The United States condemns in the strongest terms today’s horrific attack in Kenya by the terrorist group al-Shabab against innocent civilians,” Bernadette Meehan, the spokeswoman for the National Security Council in Washington, said in a statement.

The bus traveling to the capital Nairobi with 60 passengers was hijacked about 30 miles from the town of Mandera, near Kenya’s border with Somalia, said two police officers who spoke on the condition of anonymity because they were ordered not to talk to reporters.

The attackers first tried to wave the bus down, but it didn’t stop. The gunmen then sprayed it with bullets, police said. When that didn’t work, they shot a rocket-propelled grenade at it, the officers said.

The gunmen took control of the vehicle and forced it off the road, where they ordered all the passengers out of the vehicle and separated those who appeared to be non-Muslims — mostly non-Somalis — from the rest.

Douglas Ochwodho, one of the passengers, told the Associated Press that the non-Somali passengers were then asked to recite the Shahada, an Islamic creed declaring oneness with God. Those who couldn’t recite the creed were ordered to lie down and were shot.

Ochwodho, a non-Muslim head teacher of a private primary school in Mandera, said he was ordered to lie down but wasn’t killed because of confusion among the gunmen. Seventeen of the 28 dead were teachers, according to a police commander.

Kenya has been hit by a series of gun and bomb attacks blamed on al-Shabab, who are linked to al-Qaeda, since Kenyan troops entered Somalia in October 2011. Authorities say there have been at least 135 attacks by al-Shabab since then, including the assault on Nairobi’s Westgate Mall in September 2013 in which 67 people were killed.

— Associated Press