A brief counter-offensive to retake Tikrit, north of Baghdad, on the day of the opening of parliament on 1 July failed to make any ground. Tikrit is without water and electricity and has been largely abandoned by its people.

Iraq’s autonomous Kurdish region looks set to take advantage of the turmoil to declare an independent state. The region’s President, Massoud Barzani, asked the parliament prepare to hold a referendum on independence, saying “the time has come for us to determine our own fate”.

Meanwhile, Isis has been securing control of the territories it has conquered in Iraq and Syria and has declared them subject to a caliphate called the Islamic State. After two days of negotiations in Mosul it has told its militant allies, who had helped it to drive out the Iraqi army, that they must pledge allegiance to the Islamic State and give up their weapons.

As a result, tribal and Sunni militants who are not part of Isis are less likely to be able to oppose the jihadis or split from them, as happened in 2006-07 when the US-backed Sahwah movement divided the Sunni insurgency.

In declaring the Islamic State and demanding that all Muslims pledge allegiance to it, Isis has challenged the legitimacy of all Muslim rulers – including those of Saudi Arabia, Jordan and Turkey, who have fostered the opposition in Syria and been sympathetic to it in Iraq.

Studies show that where Isis takes over a district it can often recruit five or 10 times the number of fighters it used to secure control. It is offering about £400 a month for recruits with military experience, and Iraq is full of jobless young men of military age.

Iraq is also facing a political crisis as it tries to form a new government after the parliamentary election on 30 April. Nouri al-Maliki, the Prime Minister, did well in these by presenting himself to Shia voters as a man who was tough on security and who knew how to cope with a Sunni counter-revolution. Discredited by military defeat and loss of control of most of the country north and west of Baghdad, Mr Maliki still clings to power.

He is helped by the deep divisions within the Shia, Sunni and Kurdish communities, which have not been able to pick which of their leaders should be chosen as candidates. The speaker of parliament is normally a Sunni, the president a Kurd and the prime minister a Shia, but no decision on choosing them is likely within the next three or four weeks, say MPs. After the 2010 election it took 10 months to choose a new government.

Talks on forming a national government will continue inside the heavily defended Green Zone.

PATRICK COCKBURN is the author of Muqtada: Muqtada Al-Sadr, the Shia Revival, and the Struggle for Iraq.