An explosive device underneath a rental car detonated in the border city of Tornio, Lapland early on Tuesday morning, according to local authorities.
The rental car was hired for use by the Finnish Border Guard.
The explosion took place in the city's Pudas residential neighbourhood on Aarnintie street, an area that features blocks of flats.
An investigation into the suspected blast is still in early stages and the Lapland police department has not issued further information about the incident. Police did not disclose whether anyone was injured in the blast.
Tornio resident Tatu Savikurki said he heard a "very loud bang" at about 1 am.
"The first thing I thought was that it couldn't be fireworks, but either that a gun had been fired or something had exploded," Savikurki said, who added he did not see exactly where the explosion occurred and that he did not know what happened in any detail.
"I saw a Border Guard vehicle in front of an apartment building's front door and there were also armed police there," he said.
Authorities are currently seeking information from potential eyewitnesses concerning individuals or vehicles that were seen in the vicinity around the time of the explosion, which took place between 12-1 am on Tuesday, 4 August.
Such information can be forwarded to the Lapland police department by telephone at 02 95 466 481 or email at firstname.lastname@example.org.