Baghdad/Washington: Ruthless jihadists spearheading a Sunni militant offensive in Iraq have declared an "Islamic caliphate" and ordered Muslims worldwide to pledge allegiance to their chief, in a move the US dismissed as meaningless.
Iraqi forces meanwhile pressed a counter-offensive Monday against executed dictator Saddam Hussein's hometown of Tikrit, one of a string of towns and cities overrun by jihadist-led fighters in a swift advance that left nearly 2,000 people dead this month, displaced hundreds of thousands and piled pressure on Prime Minister Nuri al-Maliki.
Maliki's bid for a third term in office has been battered by the offensive and he is no longer seen as the clear frontrunner when the new parliament elected in April holds its opening session on Tuesday.
A security source based near Tikrit said reinforcements had arrived with tanks and artillery on Monday.
An army officer said troops controlled parts of the outskirts of the city, some 160 kilometres (100 miles) north of Baghdad, which the militants captured on June 11.
The Islamic State of Iraq and the Levant renamed itself simply the Islamic State (IS) and declared its shadowy frontman the leader of the world's Muslims, in a clear challenge to Al-Qaeda for control of the global jihadist movement.
IS announced on Sunday that it was establishing a "caliphate" -- an Islamic form of government last seen under the Ottoman Empire -- extending now from Aleppo in northern Syria to Diyala province in eastern Iraq, the regions where it has fought against the regimes in power.
In an audio recording posted online, the group declared its chief Abu Bakr al-Baghdadi "the caliph" and "leader for Muslims everywhere". Henceforth, the group said, he is to be known as "caliph Ibrahim" -- a reference to his real name.
'Sense of ambition'
Although the move may not have immediate significant impact on the ground, it is an indicator of the group's confidence and marks a move against Al-Qaeda -- from which it broke away, analysts say.
"I don't think this materially changes anything," said Shashank Joshi, research fellow at the Royal United Services Institute think tank in London.
"What it really changes is the sense of their ambition. It's a potentially inspiring and invigorating movement for people worldwide.
"It will tempt many radicalised Muslims to join their cause."
Baghdadi, thought to have been born in the Iraqi city of Samarra in 1971, is touted by the group as a battle-hardened tactician who fought American forces following the US-led invasion of 2003, and is now widely seen as rivalling Al-Qaeda chief Ayman al-Zawahiri as the world's most influential jihadist.
His group has drawn thousands of foreign fighters, attracted by a combination of Baghdadi's own appeal, IS's efforts to establish what it believes is an ideal Islamic state, and the group's sophisticated propaganda apparatus, which publishes magazines and videos in English and a host of European languages.
The group is known for its brutality; summarily executing its opponents and this week crucifying rival Islamist rebels in Syria.
In Syria, IS fighters control large swathes of territory in Deir Ezzor near the Iraq border, Raqa in the north, as well as parts of neighbouring Aleppo province.
In Iraq, it has spearheaded a lightning advance since June 9, capturing sizeable territories in the north and west, including the country's second city Mosul.
'No meaning'
Washington, however, said the caliphate declaration had "no meaning", with State Department spokeswoman Jen Psaki telling reporters that it just "exposed the true nature of this organisation and its desire to control people by fear."
Iraqi forces initially wilted in the face of the onslaught but have mounted an ambitious counter-offensive to take back Tikrit, a battle which could be crucial tactically and for the morale of the security forces.
They have nevertheless suffered heavy casualties, with 380 soldiers among the nearly 2,000 people who died this month, the highest death toll since May 2007, according to figures released by Iraqi ministries.
In May 2007, Iraq was in the throes of a brutal sectarian war between the Shiite majority and the Sunni Arab minority that claimed tens of thousands of lives.
But Maliki's national reconciliation adviser, Amr Khuzaie, said the current crisis was even more dangerous.
"Now, the danger is definitely more... than 2006, 2007," he told AFP.
World leaders and leading clerics have pressed Iraqi leaders to unite and quickly form a government, but despite the urgency, politicians have warned that the process of choosing a new prime minister could take more than a month.
Declaring 'caliphate' in Iraq, Syria has 'no meaning': US
The United States said Monday the declaration by Sunni militants of an "Islamic caliphate" on territory they have seized in Iraq and Syria has "no meaning."
"We have seen these types of words or comparable claims from ISIL before," State Department spokeswoman Jen Psaki told reporters, referring to the Islamic State of Iraq and the Levant militant group.
"This declaration has no meaning for the people in Iraq and Syria," she said, adding that it just "exposed the true nature of this organization and its desire to control people by fear."
The militants, who have seized a large swath of territory in northern and western Iraq and also control areas in neighbouring Syria, have now renamed their group the Islamic State.
"This is a critical moment for the international community, for countries in the region, for all of the Iraqi people to unite against the threats that they face," Psaki said, while stressing she did not want to "overemphasize" the declaration's impact.
The White House said the jihadists spearheading the offensive in Iraq had waged "a campaign of terror of gross acts of violence and repressive ideology that pose a grave threat to Iraq's future."
"ISIL is not fighting for a stronger Iraq. ISIL is fighting to destroy Iraq. And that's why you've seen this administration work closely with Iraq's political leaders to encourage them to unite the country as they confront this existential threat," spokesman Josh Earnest said.
With Iraq's parliament scheduled to hold its opening session Tuesday following April elections, Psaki said Washington was "continuing to urge Iraqi leaders to come to an agreement on the three critical posts that are key to forming Iraq's next government."
In an audio recording released online Sunday, the militants said their caliphate would spread from Aleppo in northern Syria to Diyala in eastern Iraq, and ordered Muslims in those areas to "obey" and pledge allegiance to their new leader.
