Sunni insurgents who battled American soldiers in Iraq until their long-time enemy withdrew last year have turned their wrath on a new target: Shiite Iran.

The fall of Saddam Hussein's regime on April 9, 2003, the dissolution of the Iraqi army and ruling Baath party and the rise to power of Shiites after 80 years of Sunni domination, buoyed Iraqi and Arabi jihadists.

Four months after most US troops left Iraq, the jihadists had to find a new reason to sustain their continued presence -- enter Iran and the Shiite-led Iraqi regime.

"Armed groups always need to find an enemy in order to justify their existence," said Hamid Fadel, a professor of political science at Baghdad University.

In the run-up to the 9th anniversary of the fall of Saddam's regime and the start of US occupation, militant groups issued a plethora of statements attacking Iran and Shiites.

The Islamic Group in Iraq, a coalition of 17 insurgent groups formed in 2010, said in a statement that "we will fight Iran with the same force that we fought their brothers, the Americans."

The United States was "forced" to leave Iraq "to a worse occupier, the greedy Persian coward," said the statement posted on jihadist websites.

"It has become clear beyond any doubt that Iran occupies Iraq through its traitor agents," it added.

The statement played on the centuries-old hostility between Arabs and Persians, as well as the outrage of Sunnis in Iraq who lost their power to the majority Shiites after the 2003 US-led invasion.

That anger is reinforced by the fact that some of Iraq's current leaders lived in exile in Iran during the 1980-1988 war between the two countries.

Another group of jihadists, the Banner of Right and Jihad, vowed to continue "fighting the enemy" and urged God to grant it victory over "America and its (followers) the Safavids," in a derogatory reference to Shiites.

For its part, the Murabitun Jihad Brigades asked for God's blessing in securing "a final victory over the (followers) of the occupation and its agents represented in the government" of Iraq.

And the Islamic Army in Iraq said the US left "behind them an uglier, more brutal and ignorant occupation, where the graves are full of the innocent bodies of Sunnis."

The Islamic State of Iraq (ISI), Al-Qaeda's front organisation, said that it had carried out 195 attacks against "the Safavid army and police" between December 28 and February 24.

Fadel said the new strategy of Sunni insurgents has a "regional dimension."

"The majority of the groups that portray Iran as the enemy are probably in contact with countries in the region that are in conflict with Iranian politics, or with the Baath party, which rejects the political process," Fadel said.

Izzat Ibrahim al-Duri, Saddam's vice president and the highest-ranking member of his regime still on the run, poured oil on the fire in a video posted online last week,

Duri charged that that Iran plans on "taking over Iraq and then destroying the nation."

Meanwhile, Shiite armed groups who also battled the US "occupiers" now face no opponent and have decided to enter politics.

Asaib Ahl al-Haq, or the League of the Righteous, which has been accused of killing US troops, announced in December that it would join the Iraqi political process.

And Jawad al-Hasnawi, an MP from the Sadr movement whose Mahdi Army armed fought pitched battles against American and Iraqi forces, told AFP "the number one enemy of the Sadrist movement now... is corruption, unemployment and dictatorship."