STOCKHOLM (Reuters) - A Swedish asylum center burned down overnight in a suspected attack by arsonists, police said on Friday, the second incident of its kind in a week in the Stockholm region.

Staff alerted police in the early hours of Friday after hearing noises and seeing lights outside the building, Stockholm police spokesman Kjell Lindgren said.

A fire then broke out, he said, adding police had opened an investigation. "Things do not just catch fire outside (a house) for no reason."

Two staff and nine residents were at the center at the time of the blaze, during which no one was hurt, Lindgren said.

Sweden reversed decades of generous immigration policies last year, introducing border controls and tougher laws after an a record number of asylum applications that coincided with unprecedented flows of refugees entering Europe to escape war and poverty in Africa and the Middle East.

Police have been keeping a close watch on the country's asylum centers, several of which have since been attacked, including one in southern Stockholm that caught fire early last Sunday.

No one was injured either in that blaze, which led to 37 residents being evacuated.

Lindgren said there was no indication the two fires were linked, or that the risk of attacks against asylum centers had increased.

(Reporting by Simon Johnson; editing by John Stonestreet)