Police officer Ted Eriksson is treated in Stockholm last summer after he was stabbed in the neck by an asylum seeker

The blast was so powerful that it shook windows a mile away. Ahmad’s first thought was that someone had thrown yet another bomb at the police.

He was right. On Wednesday night an explosive device was hurled at the police station in Rosengard, a troubled area of Malmo, Sweden’s third largest city.

Attacks on the police are increasingly frequent. Rosengard’s force works from a black fortress of reinforced concrete with narrow windows and a 10ft-high electric fence.

“I knew it was a bomb again,” said Ahmad, 53, who lives in the area with his wife and their four teenage children.

Sweden is among the world’s safest, richest and best-run countries enjoying steady growth and rising employment. But it has been experiencing an unprecedented surge of