Swedish police are investigating an attack on a mosque with a homemade bomb as a hate crime, officers said Monday.

The attack on the Islamic Cultural Center in Saffle, a town 45 kilometers (28 miles) southwest of Karsltad, left ball-bearings lodged in the walls of the center's prayer room.

Broadcaster SVT reported that police had completed a preliminary investigation and were treating the attack as a hate crime.

"Windows were broken and the walls were hit by explosives reinforced with BB pellets," center Chairman Abdihakem Adan said.

"An average of 100 people come to the mosque and pray every day."

Sweden is a strong draw for many migrants and about 15 percent of its population was born abroad. An estimated 100,000 ethnic Turks live in the Nordic country.