A police spokesman said they were taken to hospital with injuries from smoke inhalation to lacerations.

Local media footage showed flames billowing from the windows.

The attack comes amid an intense debate over immigration. The arson attack happened on Christmas Day amid tense a debate in Sweden on immigration and increasing support for the Sweden Democrats, a far-right political party.

The far-right and anti-immigration Sweden Democrats gained 13 percent of the votes in the September elections. This more than doubled its support since the last parliamentary elections in 2010 and made the party the kingmakers of the Parliament.

In related news, Swedish ministers have condemned Thursday's arson attack on a mosque in the southeastern Swedish town of Eskilstuna, which injured five people.

''[This is] foul,'' Interior Minister Anders Ygeman told the Swedish news agency TT on Thursday. ''We are not doing enough to protect regardless of whether it is a mosque or other religious communities,'' he added.