STOCKHOLM (AFP) - Sweden's largest Shi'ite Muslim mosque was badly damaged overnight in a suspected arson attack, police said on Monday (May 1).

"Flames were engulfing the outer facade" of the Imam Ali Islamic Centre in the northern Stockholm suburb of Jakobsberg, a police spokesman said, although there were no reports of any injuries.

"It seems it was set ablaze from the outside," the TT news agency quoted police spokesman Lars Bystrom as saying, adding an investigation was under way to determine if the motive was political.

"This is Sweden's largest Shia mosque with thousands of faithful... They are really concerned," mosque spokesman Akil Zahari told broadcaster SVT.

Several mosques in Sweden have been the target of arson attacks in recent years but few perpetrators have been caught.

In April last year, a 31-year-old man identified through CCTV footage was jailed for three years for racially-aggravated arson after admitting setting fire to a mosque in the south-western town of Boras.

Swedish anti-racism campaigners protested in January 2015 after a trio of arson attacks on mosques in the Nordic country.

In Stockholm, residents are still coming to terms with an April 7 truck attack which killed five people.

An Uzbek national confessed to using a stolen truck to mow down pedestrians on a busy shopping street in a rampage similar to attacks in Nice, Berlin and London.