At least six people were killed as gunmen attacked two buses on Friday in Kenya’s north-eastern region of Mandera, near the Somalia border.

The identity of the assailants is not yet known, but attacks carried out by Al Shabaab are frequent in that volatile region.

In November 2014, a bus was attacked near Mandera by militants, who killed 28 non-Muslims travelling to Nairobi for the Christmas holidays. In a similar incident in December 2015, at least two died.

In December 2014, 36 quarry workers, believed to be Christians, were slaughtered.

In all incidents, militants separated their victims from Muslims before shooting them dead.

The majority of the local population in north-eastern Kenya are Muslims of Somali descent. Unlike the rest of Kenya, Christians form a minority and constitute the primary target of the Somali militant group. In the attack at the local Garissa University, the militants made a claim on the north-east, saying non-Muslims should vacate what they described as “colonised land”. The attacks have instilled fear among the Christian community: large numbers have fled from the area, including about 2,000 teachers.

North-eastern Kenya is experiencing a clear case of ethnic cleansing on religious grounds, according to a report in February 2016 by Open Doors International, a charity which supports Christians under pressure for their faith.

Al-Shabaab has been at war with Kenya ever since Kenyan forces entered Somalia in October 2011 in an effort to crush the militants.