Sweden mosque attack
Firemen work as smoke billows from the windows of a mosque in Eskilstuna December 25, 2014.Reuters

A mosque in Sweden was set on fire allegedly by an arsonist on Thursday, celebrated worldwide as Christmas day, leaving five people injured. 

About 20 people were inside a mosque in Eskilstuna used mainly by Somali Muslims, when the fire broke out during noon prayers , forcing evacuation in nearby buildings as well.

The fire was said to be caused by an arsonist, as witnesses claim that a suspect threw an object at the mosque. 

"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, according to Deutsche Welle.

Two people were injured due to smoke inhalation, while three suffered bodily injuries. 

Muslims in the country have complained of increasing tension.

"There has been an intensification of hatred against Muslims," the head of Sweden's Islamic Association, Omar Mustafa, said on the public radio.

Earlier this year, the front door of a Stockholm mosque was defaced with  black swastikas.

The attack comes even as the country is seeing a heated debate on the issue of immigration.

Tensions have risen among immigrants after the Sweden Democrats, seen as being anti-immigration, brought down the government earlier this month by refusing to support the budget in Parliament.

Snap elections have been issued for March next year, and the Sweden Democrats have vowed to turn it into a 'referendum on immigration'.