Iraq crisis: Helicopter strikes on Tikrit rebels

Helicopter gunships have conducted strikes on the northern Iraqi city of Tikrit, the BBC reported, citing the Iraqi military. 

The attacks come amid reports of a major offensive to retake Tikrit from Isis-led Sunni militants, who control large parts of north and west Iraq.

The news came hours after the US confirmed it was flying drones in Iraq, to protect US personnel on the ground.

Meanwhile Iraq's most influential Shia cleric has called for a prime minister to be appointed by Tuesday.

In an attempt to defuse the country's political crisis, Grand Ayatollah Sistani said that key positions should be agreed before the new parliament meets on Tuesday.

Pressure has been building for a national unity government.

Current Prime Minister Nouri Maliki wants to continue for a third term, even though 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.

The air strikes targeted Sunni insurgents attacking troops who have established positions in a university campus to the north of Tikrit, military spokesman Lt-Gen Qassim al-Moussawi was quoted as saying by the Associated Press.

Tikrit, the birthplace of former Iraqi leader Saddam Hussein, is a mainly Sunni city which fell to militants led by Isis - the Islamic State in Iraq and the Levant - in recent weeks.

Unconfirmed reports say that thousands of troops are advancing on the city from nearby Samarra, backed by aircraft, tanks and bomb disposal units.

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