A police spokesman said a man died after picking up an object outside the Varby Gard station in Stockholm.
The Varby Gard station, in the Huddinge residential district in southwest Stockholm, was closed off for investigation.
A man in Stockholm picked up a suspected hand grenade from the ground and it detonated in his hand Sunday, killing him and injuring his companion, Swedish police said.
Police told news agency TT that the killed man and the injured woman were a couple.
Police declined to confirm that report, for which the newspaper named no sources.
The deceased, a 60-year-old man, had been taken to the hospital with serious injuries after an object he picked up off the ground exploded.
"Someone has used some kind of explosive".
"We're suspecting that it's a hand grenade of some sort, " Lars Alvarsjo, chief of Stockholm's southern police district, told the Swedish national broadcaster SVT.
On Sunday morning, police searched the area around the station, which was cordoned off as a bomb squad was called in to carry out an investigation.
So far, police did not say whether the explosion was a terror-related incident.