"We have seen violence that we have to condemn," he told a news conference after talks with Swedish Foreign Minister Carl Bildt.
"We expected that the election process would be something clearly positive for the international community. Unfortunately what we have seen today is something very different."
Iranian authorities said earlier on Tuesday they would teach a lesson to "rioters" detained after the worst unrest to befall the country since the 1979 Islamic Revolution.
Hundreds have been detained by police to clamp down on protests triggered by results of a June 12 election that gave President Mahmoud Ahmadinejad a landslide victory.
Bildt said Sweden, which is due to assume the revolving EU presidency on July 1, had called the Iranian ambassador on Tuesday to condemn the clamp-down by authorities as well as the use of violence against peaceful demonstrators.
