President Barack Obama on Tuesday said the world was “appalled and outraged” at Iran’s crackdown on protesters and added that many Iranians saw the country’s recent election as illegitimate, in his toughest language so far on the crisis in the Islamic republic.

His condemnation, at a press conference in the White House, follows days in which conservative critics in the US have called on him to take a more forceful approach, even as the clampdown in Iran has intensified.