President Bush has called the execution of former Iraqi dictator Saddam Hussein an "important milestone" for Iraq on its path to becoming a democracy that can govern, sustain and defend itself.
Mr. Bush says Saddam's death marks the end of a difficult year for the Iraqi people, but warned it "will not halt the violence in Iraq."
Iraqi Prime Minister Nouri al-Maliki urged Saddam's fellow Sunni Baathists without what he called "innocent blood on their hands," to help rebuild Iraq.
Britain said Saddam had been "held to account" for some of his crimes against the Iraqi people. France called on Iraqis to work toward reconciliation and national unity.
Other countries opposed to capital punishment, including India and Russia, warned the execution could lead to a fresh wave of violence and further instability in the region.
The Vatican condemned Saddam's death as a "tragic event."
Kuwait hailed the execution as fair and just. Iran called it a "victory for the Iraqi people."
The Hamas-led Palestinian government denounced Saddam's hanging, and Libya declared three days of official mourning.
Saddam's lawyers and some human rights groups say the ousted Iraqi dictator did not get a fair trial.
U.S.-based Human Rights Watch said Saddam's trial was "deeply flawed," and condemned the hanging as "cruel and inhuman," despite Saddam's "horrific and widespread human rights violations."
CNN television showed images of Arab-Americans celebrating and waving Iraqi flags in Dearborn, Michigan, in the northern U.S. Some of the revelers who had lost family members during Saddam's brutal regime said they viewed the execution as an act of justice and revenge, and expressed hope the former dictator's death would result in peace in Iraq.
Street celebrations also were reported in Baghdad's Shi'ite Sadr City slum and other predominantly Shi'ite areas.
Some Iraqis say they consider Saddam's death revenge, but they expect his execution will lead to an increase in violence, at least in the short term.
Some information for this report was provided by AP, AFP and Reuters.