A pair of explosions in central Stockholm, Sweden, was "an act of terrorism," a Swedish police official said Sunday.
Two explosions occurred within minutes of each other Saturday in the district full of Christmas shoppers, Swedish authorities said.
A Swedish news agency and police said they received e-mailed threats 10 minutes before the explosions, which killed one person and injured two others.
Swedish authorities have not confirmed the three events are connected, Prime Minister Fredrik Reinfeldt said Sunday.
But he called the explosions "completely unacceptable."
"It is completely unacceptable that a man walks around with a large quantity of explosives on him," Reinfeldt said. "This is not the path we want to go down. It is very serious that this has already happened."
And he mounted an impassioned defense of Swedish society in the face of what seems to be its first suicide bombing.
"Sweden is an open society," Reinfeldt said. "It is an open society which has demonstrated a will that people must be able to come from different backgrounds, believe in different gods or not believe in any god at all. Be able to live side by side, together, in our open society."