Kenyan authorities have stepped up security after al Shabaab militants hijacked a bus and shot dead 28 non-Muslims.
They have also responded to the killings with airstrikes, claiming to have destroyed one of the group’s camps in Somalia and killing around 45 militants.
The bus passengers, who were travelling to Nairobi, were “brutally executed” by the Islamic extremists, a police officer said.
His colleague claimed that the 60 people on board were told to disembark, and asked questions about the Koran.
Those who could not recite an Islamic declaration were shot at close range, according to the officers.
Nine of the victims were women and 19 were men. Some of the dead were public servants heading to Nairobi for the Christmas holiday, the officers said.
Only one person who was targeted survived the atrocity, apparently after both gunmen thought they had shot him.
Al Shabaab claimed responsibility for the killings saying they were in retaliation for recent raids by Kenyan security forces on four mosques on the Kenyan coast.
The bus attack took place in Mandera, a town on the border between Kenya and Somalia. An estimated 20 Islamist militants were involved.
According to a regional police chief, the extremists were planning to drive the non-Muslims into Somalia, but the bus became stuck.
Al Shabaab, a well-known terror organisation, was also responsible for the attack on the Westgate shopping mall in Nairobi, which left 67 people dead.
The group, which has been fighting to topple Somalia’s government, said last September’s massacre was in retaliation to the continued presence of Kenyan troops in the warring country.
Foreign Office Minister Hugo Swire condemned terrorist attack in Kenya and pledged continued UK support for the fight against al Shabaab.
He said: “I strongly condemn the attack that took place in Mandera county, Kenya, today, killing 28 people. I offer my condolences to the families and loved ones of those who died.
“There can be no place for such senseless acts of violence in our societies.
“The UK stands by the Kenyan government in its fight against terrorism and in its efforts to bring those responsible for this barbaric act to justice.”