Iraqi forces battled Islamic State (IS) group fighters Saturday in Ramadi, where a fierce jihadist offensive threatens one of the last pockets in Anbar province still under government control.

"Fierce fighting pitting security forces and tribal units against IS is taking place in the Al-Hoz, Muallimin and Bakr neighbourhoods," a police major told AFP.

"The clashes have been going on for several hours," he said, without specifying how many casualties the violence had claimed.

Al-Hoz district, in the south of the Anbar provincial capital, fell to IS during the past week of fighting in Ramadi, a large city on the Euphrates 100 kilometres (60 miles) west of Baghdad.

Sheikh Omar al-Alwani, the leader of one of the Sunni tribes opposing the jihadists and fighting alongside the government in Anbar, said slow military progress was being made.

"The army and tribal fighters are advancing slowly in Al-Hoz today. They control the entrances to the neighbourhood," he told AFP by phone.

"There are many booby-traps and we don't have a bomb disposal unit with us so we can only take position in a house once we have tossed a hand grenade in it to see if it is rigged with explosives," he explained.

"If the army stays with us, we can claim back the entire neighbourhood soon," he said, adding that Iraqi air raids had destroyed IS sniper positions and armoured vehicles on Saturday.

Police and army officers said that a partial curfew was in place in Ramadi and that reinforcements had been deployed to protect the main government compound in the city.

Parts of Ramadi and all of Fallujah, to its east, have been outside government control since the beginning of the year, but much more of Anbar province has since been seized by IS, which spearheaded a sweeping June offensive that overran swathes of Iraq.