Police said between 15 and 20 people were in the mosque in the Swedish town of Eskilstuna when the fire broke out at around noon on Thursday. Of the five injured, two were treated for smoke inhalation, two suffered lacerations and one a foot injury.

Police said they were treating the fire, which forced the evacuation of several nearby apartments, as an arson.

"A witness saw somebody throw an object through the window of the building, which serves as a mosque, after which a violent fire began," police spokesman Lars Franzell said.

There was no word on the possible identity of the suspect and there was no immediate claim of responsibility. The mosque is used primarily by Somali Muslims in the town, according to the KNA news agency. Eskilstuna is located about 90 kilometers (56 miles) west of Stockholm.

Political debate over immigration

The apparent arson attack comes amid a growing political debate over immigration in the country, which has traditionally been seen as welcoming to immigrants.

Three weeks ago, the far-right Sweden Democrats party brought down the two-month old government of Social Democrat Prime Minister Stefan Lofven by refusing to support his budget in parliament. Lofven reacted by calling a snap election for March 22.

The Sweden Democrats who took 12.9 percent of the vote in September's general election, have vowed to turn the March vote into a "referendum on immigration." A recent YouGov opinion poll put support for the far-right party at almost 18 percent.

All of the mainstream parties have refused to work with the Sweden Democrats, but a major influx of immigrants has moved the issue higher up the country's political agenda. With a population of just under 10 million, Sweden is expected to receive a total of 100,000 asylum seekers in 2014.

pfd/sb (Reuters, dpa, KNA)