Iraq army launches offensive to retake Tikrit from Isis

The Iraqi army has been boosted by new recruits from Shia militias

Thousands of troops backed by tanks and air power are trying to dislodge Isis-led rebels who took the city two weeks ago in a lightning offensive that also captured the second city, Mosul.

The rebels have taken large swathes of the north and west.

Iraqi military sources said the Tikrit offensive was being coordinated with American military advisers.

However, although the US has confirmed it is flying armed drones in Iraq to protect US personnel on the ground, US officials say American troops are not directly involved in the hostilities.

Reda El Mawy reports on the Christians fleeing Qaraqosh

Separately, Iraq's most influential Shia cleric called for a prime minister to be appointed by Tuesday to try to defuse the country's political crisis.

Grand Ayatollah Sistani said key positions should be agreed before the new parliament meets then. Pressure has been building for a national unity government.

Prime Minister Nouri Maliki wants a third term, though correspondents say he is seen by many as having precipitated the crisis through sectarian policies that have pushed Iraq's Sunni minority into the hands of Isis extremists.

'Flee or be killed'

The BBC's Jim Muir, who is in northern Iraq, says that since Tikrit fell to rebels of the Islamic State in Iraq and the Levant (Isis) on 11 June, the government has been threatening a counter-offensive from the next town down the Tigris river - Samarra - where the insurgents were finally checked.

Now soldiers supported by allied Sunni tribesmen and Shia militias have advanced on Tikrit - the mainly Sunni hometown of former leader Saddam Hussein - from the south and west.

Air strikes targeted insurgents at a university campus to the north of Tikrit and in other areas of the city.

Soldiers captured part of the university campus in a helicopter operation on Friday.

Iraqi Shia fighters secure an area to the west of the city of Najaf

Several air strikes were also reported on the rebel-held second city of Mosul

A rebel spokesman said one helicopter gunship was shot down.

The success of the offensive is so far unclear and there is no word on casualties.

One Iraqi official told Associated Press (AP) progress was slow.

However, army spokesman Lt-Gen Sabah Fatlawi told AFP news agency: "Isis fighters now have two choices - flee or be killed."

Residents said militants were still patrolling the city.

One citizen, Muhamad Saif al-Din, told AP the city had become a "ghost town" as people fled in fear of extensive fighting.

He said: "The few people who remain are afraid of possible revenge acts by Shia militiamen who are accompanying the army. We are peaceful civilians and we do not want to be victims of this struggle."

Another army spokesman, Lt Gen Qassem Atta, told AFP that Iraqi forces were also now in control of a key road from Baghdad to Samarra.

He said there was coordination with the US over "studying important targets".

The US is deploying some 300 military advisers to Iraq, but says its aircraft and drones will not be used in military combat.

Meanwhile, the Archbishop of Irbil in northern Iraq told the BBC that more than 40,000 Christians had fled villages near Mosul in recent days after insurgents attacked the two large Christian settlements of Karakosh and Karamlaish.

The displaced have sought refuge in the Kurdistan region of Iraq.