The bus was headed to the city of Mandera, near the border with Somalia and Ethiopia.
The journey is such a security risk that most buses travel with a police escort.
In this case, however, the police car broke down and the bus continued on its journey, Joseph Nkaissery, Kenya’s interior cabinet secretary, said.
A few hours later, the militants attacked.
Al-Shabaab, a Somali group the United States has designated as a foreign terrorist organization, wants to turn Somalia into a fundamentalist Islamic state. It has launched a series of attacks in Kenya, since Kenyan forces went into Somalia to battle the extremists in 2011.
Its goal: sow division in the border regions of Kenya and Somalia, where many of the people are ethnically Somali, analysts say.
Among Al-Shabaab’s most brutal acts was the raid on Garissa University College in April that left nearly 150 people dead. Witnesses described how gunmen asked students to …