WASHINGTON -- President Barack Obama on Tuesday declared the United States and the entire world are "appalled and outraged" by Iran's violent efforts to crush dissent, a clear toughening of his rhetoric as Republican critics at home pound him for being too passive.

Obama condemned the "threats, beatings and imprisonments of the last few days. "

"I strongly condemn these unjust actions," Obama said in a news conference at the White House.

In Tehran, chaotic images of riot police beating and shooting protesters have seized the world's attention and heightened pressure on Obama to act - or at least speak out more strongly.

At least 17 people have been killed in protests since the election last week.

Protesters in Iran have demanded that the government there cancel and rerun the elections that ended with a declaration of overwhelming victory for hardline President Mahmoud Ahmadinejad. Reformist presidential candidate Mir Hossein Mousavi says he won and has claimed widespread fraud.

"I have made it clear that the United States respects the sovereignty of the Islamic Republic of Iran, and is not interfering in Iran's affairs," Obama said. "But we must also bear witness to the courage and dignity of the Iranian people, and to a remarkable opening within Iranian society. And we deplore violence against innocent civilians anywhere that it takes place."