A man died after he picked up a suspected hand grenade and it detonated, killing him and injuring his companion, Swedish police said.

The blast took place on Sunday at about 1100 local time [1000 GMT] just outside the Varby Gard subway station in Huddinge, a residential district in greater Stockholm, said regional police spokesman Sven-Erik Olsson.

The man, who was in his 60s, was rushed to hospital while a woman, in her mid-40s, received “minor wounds” to her face and both legs.

“The man was seriously injured after he picked up something from the ground and this device exploded,” Mr Olsson said.

Police officers cordon off the area outside Varby Gard metro station (TT News Agency/Henrik Montgomery/via Reuters) (TT News Agency/Henrik Montgomery/via REUTERS)

Police said fragment damages on the victims and findings at the scene indicated the explosive could be a hand grenade, possibly an old one.

“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.

Mr Alvarsjo said Swedish police have “unfortunately” noticed a rise in the use of hand grenades by criminal groups in the Nordic country. The three biggest cities in Sweden – Stockholm, Goteborg and Malmo – have seen several violent gang-related incidents in the past few years. Many of the illegal hand grenades found in Sweden are being imported from former Yugoslav nations, he said.

“I heard a huge bang,” a local resident told Aftonbladet.

The Varby Gard underground station and an adjacent square have been closed while a bomb disposal squad carry out checks (TT News Agency/Henrik Montgomery/via Reuters) (Reuters)

Police said the station and surrounding area were cordoned off while a bomb disposal squad carried out checks.

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Police were initially investigating the explosion as an attempted murder, but later said there was no reason to believe the couple were targeted.

Mr Olsson said nothing indicated the event was terror-related.