Iraq said it received the first batch of Sukhoi warplanes from Russia as it pressed a counter-attack today against Sunni militants whose offensive threatens to tear the country apart.

The arrival of the fighter jets comes with Iraqi forces, backed by aerial cover, pushing to retake the militant-held city of Tikrit and world leaders urging a speeding up of government formation following elections in April.

The newly-purchased Su-25 ground attack jets are expected to be pressed into service as soon as possible, bolstering Iraq's air power as it combats a sweeping offensive by militants, led by the jihadist Islamic State of Iraq and the Levant, that has killed more than 1,000 people and sparked a humanitarian crisis with hundreds of thousands displaced.

But it remains unclear who will fly them -- executed dictator Saddam Hussein's air force had Su-25s, but even if they were both trusted and willing, those pilots are unlikely to have had time in the aircraft in more than a decade.

Iraqi Prime Minister Nuri al-Maliki on Thursday announced that Baghdad was buying more than a dozen of the warplanes from Russia in a deal that could be worth up to USD 500 million (368 million euros).

While Washington has begun sending military advisers to help Iraqi commanders and is flying armed drones over Baghdad, Iraqi officials have voiced frustration that multi-billion dollar deals for US-made F-16s and Apache helicopters have not been expedited.

Iraqi forces have for days been pressing a campaign to retake Saddam's hometown of Tikrit, which fell to the militants on June 11.

Thousands of soldiers, backed by tanks and bomb disposal units, have been engaged in the battle for the city -- with air strikes adding firepower to the counter-offensive.

According to Maliki's security spokesman, Iraqi forces are coordinating with US advisers over "important targets" of the air attacks.

The spokesman has said hundreds of soldiers have been killed since the offensive was launched on June 9, while the UN puts the overall death toll at over 1,000, mostly civilians.

The US has publicly pushed for political reconciliation and while it has stopped short of calling for the premier to go, it has left little doubt it feels he has squandered the opportunity to rebuild Iraq since American troops withdrew in late-2011.

US officials have also said a proposed USD 500-million plan to arm and train moderate rebels in neighbouring Syria could also help Iraq fight ISIL, which operates in both countries.