One person died and another was slightly hurt Sunday in a blast outside a metro station in a Stockholm suburb, which police said did not appear to be a terrorist attack.

A man in his 60s died in hospital after "he picked up an object off the ground which promptly exploded," police spokesman Sven-Erik Olsson told AFP.

A woman aged 45 was also hurt, suffering facial injuries, police said.

The blast occurred mid-morning at the Varby gard station in Huddinge, a southern suburb of the Swedish capital.

Police cordoned off the station and the square where the blast happened as the bomb squad moved in to investigate.

The Expressen and Aftonbladet newspapers said the device was a hand grenade.

"It is too early to say. Technicians are still working on it. Nothing indicates that the (injured) couple were targeted," said Olsson, adding there was nothing to suggest an act of terrorism.

Local resident Milorad Jencic told AFP he was shocked as witnesses and onlookers gathered around the police cordon.

"We had incidents in the 1990s and early 2000s. There were very violent gangs" at the time, he said, adding he was "surprised" by this blast because he thought those groups had since disappeared.

According to a Swedish police report published last year, Sweden is the European country where criminal gangs use the most grenades, often from stocks from the former Yugoslavia.

In August 2016, an eight-year-old boy was killed by a grenade thrown into a flat in a working-class area of Gothenburg.