Die-hard jihadists made a desperate last stand Saturday in Ramadi's former government complex, the main remaining target of Iraqi forces reconquering the city they lost in May.

After a push on Tuesday that broke the Islamic State group's defences around the city centre, government forces were slowed by snipers, booby traps, roadside bombs and suicide attackers.

Initial hopes of a quick victory faded, but Iraq's elite counter-terrorism service (CTS) and the army have advanced steadily through the devastated capital of Anbar province.

They reached a key intersection in the Hoz neighbourhood, home to the government complex, whose seizure would go a long way towards ensuring a full recapture of Ramadi.

"CTS has cleared Hoz neighbourhood in central Ramadi completely and arrived near the government complex," spokesman Sabah al-Numan told AFP.

Iraq's war media cell, which speaks on behalf of the interior and defence ministries as well as the paramilitary groups fighting IS, said the jihadists' use of improvised explosive devices had forced a shift in strategy.

"The plan was to enter Hoz from Dhubbat but because of the mines, CTS changed tack and came in from the river bank," a statement said.

The latest fighting left at least two members of the security forces dead and nine wounded, according to police Captain Ahmed al-Dulaimi.

At least three were killed on Friday, according to several senior officers and local officials.

The figures they provide for IS casualties are high, with at least 23 killed on Friday alone.

The number of IS fighters hunkered down in central Ramadi was estimated at the start of the operation five days ago at no more than 400.

- Boost for military -

"You have the 8th Iraqi Army and CTS... and they're all pushing forward," said Colonel Steve Warren, spokesman for the US-led coalition supporting Iraqi forces in Ramadi with daily air strikes.

"CTS have made more progress; they're several hundred metres (yards) closer to the government complex," Warren said.

The government forces' advance has also been hampered by the possible presence of families trapped in the combat zone and used by IS as human shields.

Officials said Friday dozens of families were thought to still be in combat areas.

Civilians who escaped said after being taken by the army to camps east of Ramadi that there was little food for those left behind.

One of them said he and his family were rescued after retreating IS fighters used them as human shields to leave the city.

"More than 250 families residing in Ramadi have been able to get out of the city since the beginning of military operations" Tuesday, said Ali Dawood, an official from the neighbouring Khaldiya district.

He said some of them were in camps with other displaced people in Anbar while others headed to Baghdad or the northern autonomous Kurdish region.

According to the International Organization for Migration, Anbaris account for over a third of the 3.2 million Iraqis who have been forced from their homes since January 2014.

Government forces held off months of IS assaults in Ramadi until May 2015, when the jihadists blitzed their opponents with massive suicide car bombs and seized full control of the city.

That defeat was Baghdad's worst in the war against IS, and a victory now would provide a welcome boost to the much-criticised federal forces.

The army collapsed when IS launched a massive offensive in June 2014.

The fightback has often been laborious and poisoned by political wrangling, but Defence Minister Khaled al-Obeidi said a week ago that Iraqi forces had reclaimed half of the territory lost to IS last year.