The Islamic State in Iraq and Syria (ISIS) has declared the establishment of an Islamic state in the areas it controls and demanded allegiance from other Muslim groups worldwide.
The Sunni militant group proclaimed its leader, Abu Bakr al Baghdadi, as "caliph" - the head of the state, and said the "caliphate" stretched from Aleppo in Syria to Diyala in Iraq.
ISIS spokesman Abu Muhammad al Adnani said in an audio recording, on the first day of Ramadan: "He is the imam and khalifah (caliph) for the Muslims everywhere.
ISIS spokesman Abu Muhammad al Adnani announced the 'caliphate' "His [al Baghdadi's] authority has expanded over wide areas in Iraq and Sham [Levant]. The land now under his leadership spreads from Aleppo to Diyala."
He added: "The legality of all emirates, groups, states and organisations becomes null by the expansion of the caliph's authority and the arrival of its troops to their areas.
"Listen to your caliph and obey him. Support your state, which grows every day."
ISIS fighters overran the Iraqi city of Mosul last month in lightning action and have been advancing towards Baghdad.
ISIS has demanded allegiance from Muslims worldwide In Syria, they have captured territory in the north and east, along the frontier with Iraq.
In Iraq, they overran the Iraqi city of Mosul last month in swift action and have advanced towards Baghdad.
ISIS' declaration comes as the Iraqi government is battling to wrest back some of the territory it has lost to the jihadist group in recent weeks.
On Sunday, Iraqi helicopter gunships struck suspected insurgent positions for a second consecutive day in the northern city of Tikrit, the birthplace of Saddam Hussein around 80 miles north of Baghdad.
Iraqi troops have been involved in a fierce counteroffensive in Tikrit The Iraqi military launched a multi-pronged attack spearheaded by ground troops backed by tanks, warplanes and helicopters.
The insurgents appeared to have repelled the military's initial push for Tikrit, and remained in control of the city on Sunday, but clashes were reportedly taking place in the northern neighbourhood of Qadissiyah.
Iraqi army spokesman Qassim al Moussawi told reporters that government troops were in full control of the university and had raised the Iraqi flag over the campus.
"The battle has several stages. The security forces have cleared most of the areas of the first stage and we have achieved results," he said.
"It is a matter of time before we declare the total clearing of Tikrit."
Iraqi volunteers joining the fight against ISIS Jawad al Bolani, a security official in the provincial operation command, said the US was sharing intelligence with Iraq and has played an "essential" role in the Tikrit offensive.
"The Americans are with us and they are an important part in the success we are achieving in and around Tikrit," he said.
Washington has sent 180 of 300 American troops President Barack Obama has promised to help Iraqi forces.
The US is also flying manned and unmanned aircraft on reconnaissance missions over Iraq.
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