A man in Stockholm picked up an unknown object from the ground that detonated in his hand Sunday, accidently killing himself and injuring his female companion near a subway station, Swedish police said.

The blast took place about 11 a.m. just outside the Varby Gard subway station in Huddinge — a residential district in greater Stockholm, said regional police spokesman Sven-Erik Olsson.

"The man was seriously injured after he picked up something from the ground and this device exploded," Olsson said, adding that experts were examining the object.

The man, in his 60s, was rushed to hospital but later died while the woman, in her mid-40s, received "minor wounds" to her face and both legs, Olsson said.

The Swedish tabloids Aftonbladet and Expressen claimed the device may have been a hand grenade but Olsson dismissed that as speculation.

Police initially were investigating the incident as an attempted murder, but later said there was no reason to believe that the couple was targeted. Olsson also said nothing has indicated that terrorism was involved.

Olsson said police were scanning and sweeping outside and inside the subway station to make sure no additional explosive devices were there.