Police said firefighters worked overnight to extinguish the fire that started Tuesday at 2 .a.m. local time in Orebro, about 160 kilometers (100 miles) west of Stockholm. No one was injured in the blaze.
Mosque spokesman Jamal Lamhamdi told local newspaper Nerikes Allehanda that it was "a sad day for Muslims in Orebro and in Sweden."
Investigator Lars Bergman said the suspect, who was not identified, was arrested on suspicion of arson early Tuesday. He declined to comment on possible motives behind the fire.
Sweden has seen growing anti-migrant sentiment and an increase in xenophobic attacks as asylum-seekers flooded into the country in recent years.
In January, a fire caused major damage at a mosque near Stockholm.
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