One person has been killed and two others injured as two explosions rocked the centre of the Swedish capital, Stockholm, police say.
A car blew up near the busy shopping street of Drottninggatan, and another explosion hit nearby minutes later.
Swedish newspapers said the second blast was set off by a suicide bomber, and a local news agency said it received a threatening e-mail.
But a police spokesman told the BBC that no cause had yet been determined.
The managing editor of Swedish news agency TT told the BBC his organisation had received an e-mail shortly before the blasts that said it was now time for Swedish people to die "like our brothers and sisters".
Mats Johansson said the message was addressed to Sweden and the Swedish people.
It included references to caricatures of the Prophet Mohammed drawn by Swedish artist Lars Vilks as well as Sweden's military presence in Afghanistan, Mr Johansson said.
"Our actions will talk for themselves. As long as you do not end your war against Islam and humiliation of the prophet and your stupid support for the pig Vilks," Reuters quoted the message as saying. BBC News
