that the authorities had warned a “mock terror drill will be carried out” in posts on Facebook on Sunday night – but the message was clearly missed by many.

"It was a mock exercise," Japheth Koome, the police commander in the capital told Reuters later. "We wanted to check on alertness of emergency services."

Kenya has every reason to take terror drills seriously. In April, a group of al-Shabaab gunmen stormed a campus at Garissa University College in the east of the country, near the border with Somalia.

In pictures: Kenya Garissa University shooting Show all 10 1 /10 In pictures: Kenya Garissa University shooting In pictures: Kenya Garissa University shooting Kenya A Kenya Defense Force soldier runs for cover near the perimeter wall where attackers are holding up at acampus in Garissa Reuters In pictures: Kenya Garissa University shooting Kenya Kenyan soldiers take cover as shots are fired in front of Garissa University EPA In pictures: Kenya Garissa University shooting Kenya Students of the Garissa University College take shelter in a vehicle after fleeing from an attack by gunmen in Garissa In pictures: Kenya Garissa University shooting Kenya Kenyan police officers take cover outside the Garissa University College during an attack by gunmen in Garissa In pictures: Kenya Garissa University shooting Kenya Students gather and watch from a distance outside the Garissa University College after an attack by gunmen In pictures: Kenya Garissa University shooting Kenya Students of the Garissa University College get out of a house where they were taking shelter from an attack by gunmen