UPDATED, 15:40, 22 Nov.

International news agencies are reporting 28 people dead following an attack by suspected members of the Somali militant group Al-Shabaab on passengers travelling to Nairobi on a bus in Mandera County near the Somali border.

The gunmen are reported to have forced the bus off the road and separated out those passengers they thought were non-Muslim before killing them.

One official is reported to have said that the assailants had asked passengers to read out verses of the Koran from memory before executing those who failed.

Some of the Somalis on the bus were also shot after reportedly pleading with the gunmen to spare non-Somali passengers.

The Kenyan Red Cross said emergency workers were trying to recover bodies from the scene of the attack and security agencies are “in pursuit of the criminal gang” that carried out the attack, according to Kenya’s Interior Ministry.

The Mandera attack follows a week of heightened tension in Mombasa after security forces raided mosques in the city, saying they were being used to store weapons.

Kenya has experience a series of Al-Shabaab attacks since it sent troops to Somalia three years ago to help fight the militant group.

There was previously unrest in Mandera in June following the shooting dead of two clerics accused of belonging to Al-Shabaab. Local residents protested that the clerics had no links to the group.