According to local media, a powerful explosion occurred in a block of flats in Annedal in central Gothenburg just before 5 am. local time (GMT+2), and it affected three adjacent blocks of flats as well as started a fire.

Gothenburg-based Swedish language daily newspaper, Göteborgs-Posten (GP), reported that fire-and-rescue services officers had rushed to the scene with more than 18 units.

Local media quoting authorities reported that 25 people injured in the incident had been admitted to hospital and four of them were in critical conditions.

The Greater Gothenburg Fire and Rescue Service, which responded to the incident, said there was no natural cause behind the explosion, and it had not found any gas pipeline in the building.

Swedish Police in its website stated that rescue and evacuation efforts were underway after an explosion had occurred in an apartment building on Övre Husargatan in Annedal.

"Preliminary investigation initiated into general dangerous destruction. There are currently no suspects in the case," Swedish Police said in a statement.

Police official said that cause of the explosion was not immediately identified as raging fire was preventing authorities to enter the premise for investigation.

Gothenburg mayor Axel Josefson told local media that a number of families had been affected due to the blast and fire in Annedal residential block which had appeared to be a 'very serious' incident.