Britain said on Tuesday it was expelling two Iranian diplomats as international condemnation of Tehran reached its strongest level yet with Barack Obama questioning presidential poll results.
London Prime Minister Gordon Brown announced the expulsions after Tehran ordered two British diplomats to leave -- while at least five European Union countries called in Iranian envoys to protest against the Tehran government's crackdown.
The United States, however, again insisted it would not interfere in Iran's internal politics.
Brown said Iran had taken "the unjustified step of expelling two British diplomats over allegations that are absolutely without foundation."
"In response to that action we informed the Iranian ambassador earlier today that we would expel two Iranian diplomats from their embassy in London," he told lawmakers.
Obama flayed the Iranian regime for its crackdown on protests, but denied Washington was interfering.
He said there were "significant questions" about hardline President Mahmoud Ahmadinejad's disputed re-election and that the world was "appalled" by violence that has left at least 17 people dead.
"I strongly condemn these unjust actions, and I join with the American people in mourning each and every innocent life that is lost," Obama told a White House news conference.
"I have made it clear that the United States respects the sovereignty of the Islamic Republic of Iran, and is not at all interfering in Iran's affairs," Obama said.
"We have seen courageous women stand up to brutality and threats, and we have experienced the searing image of a woman bleeding to death on the streets.
"While this loss is raw and painful, we also know this: those who stand up for justice are always on the right side of history," he added.
France summoned Iran's envoy for the second time in a week to condemn what it called the "brutal repression" of protests.
A senior French foreign ministry official expressed "great concern with developments in Iran" and reiterated a demand that "full light be shed on the honesty of the presidential vote."
Said spokesman Frederic Desagneaux: "He reasserted our condemnation of the brutal repression of protests that have left many dead."
The Czech Republic, Finland, the Netherlands and Sweden also summoned Iranian envoys in their capitals.
Britain, Italy and Germany have each warned their nationals against travelling to Iran, with London also pulling out the families of embassy staff.
EU foreign policy chief Javier Solana and Swedish Foreign Minister Carl Bildt added to the condemnation but admitted the EU was powerless.
"We have seen violence and we must condemn it," Solana said during a joint press conference in Stockholm.
But the European Union "has no army to send (to Iran) and even if we did, it's not sure we would send it," added Bildt, whose country takes over the rotating EU presidency on July 1.
Groups opposed to President Mahmoud Ahmadinejad have staged almost daily rallies to protest at alleged fraud in the June 12 election which returned him to power.
The unrest poses the most serious challenge to the Islamic government in 30 years.
Iranian authorities have in turn accused Western governments, particularly Britain and the United States, of meddling.
UN Secretary-General Ban Ki-moon has voiced growing concern about the violence and urged "an immediate stop to the arrests, threats and use of force."
He appealed to the government and the opposition "to resolve peacefully their differences through dialogue and legal means."
Footage of the final moments of Neda Agha-Soltan, a young woman whose death during the protests has made her an opposition icon, has been flashed around the world.