Baghdad (AFP) - Iraqi Prime Minister Haider al-Abadi flew to Russia on Wednesday seeking closer military cooperation as he faces tough challenges in the fight against the Islamic State jihadist group.

Abadi, who is due to meet President Vladimir Putin on Thursday, heads a large delegation that includes several ministers and a number of civil and military advisers.

The focus will be "the development of relations between the two countries, mainly expanding the military and security cooperation, and support for Iraqi forces in the face of terrorism," Abadi's office said.

His one-day official visit comes after IS seized Ramadi, the provincial capital of Anbar, in the worst setback for the Iraqi government since the jihadists first swept across Sunni regions in June last year.

Iraqi government and allied forces have since been battling IS fighters on several fronts.

Abadi is taking all the military help he can get, with Washington leading an air campaign and supporting the reform of the army while Iran backs Shiite paramilitary groups.

Russia delivered Sukhoi fighter jets to Iraq last year, shortly after IS seized entire swathes of the country. Baghdad has also received attack helicopters from Moscow.

Amid delays in the delivery of some US weaponry that Iraq has been expecting under an agreement with Washington, Baghdad is said to be increasingly looking to Russia, China and Iran for military purchases.

Iran's defence minister arrived in Baghdad for a visit on Tuesday.