Iraq faces a "major moment of decision" in how it responds to the latest violence, the prime minister has said.

Speaking on Thursday, Tony Blair also condemned the attack on the al-Askari shrine, a holy site for Shia Islam.

The destruction has prompted a wave of anger across Iraq which has threatened to descend into civil war.

Blair condemned the attack as "an act of desperation as well as an act of desecration by the people who committed this outrage".

He said the country was facing a struggle of "democracy versus extremism and terrorism".

"The very purpose of those who desecrated the shrine is to stop the will of the Iraqi people, expressed in an election in which over 10 million of them voted, for the country to come together in a unity government," said Blair.

He added that it was important to "stand up for democracy, for liberty, whether in Iraq or elsewhere, and make sure that the terrorists are defeated".

The terrorists were "waging their campaign "in order to prevent the coming together of the parties across Iraq".

Terrorists feared that democracy would be a "huge blow" to them, he argued. "Our response has got to be, we stand up and defeat these people."

Blair praised Iraqi leaders for urging their supporters not to engage in acts of violence. It is a "major moment of decision for Iraq", he warned.

"This is a vital struggle not just for people in Iraq but for people throughout the world."

And he said it was the same struggle in the south of Afghanistan, where British troops will be deployed later this year.

"What is our objective here: To stand up for democracy against terrorism, not walk away from it."