Iraqi government forces are
advancing into the centre of the city of Ramadi, which is controlled by
jihadist group Islamic State (IS), officials say.
Security sources
told the BBC that troops and allied tribesmen, backed by air strikes,
had already retaken two districts, and entered two others.They were heading towards the main government complex, and had come up against snipers and suicide bombers.
Ramadi fell to IS in May in an embarrassing defeat for the Iraqi army.
Last month, government forces completed their encirclement of the predominantly Sunni Arab city, about 90km (55 miles) west of Baghdad, cutting off militants inside the centre from their strongholds elsewhere in Anbar province and in neighbouring Syria.
'Human shields'
Iraqi Counter-Terrorism Service spokesman Sabah al-Numani said troops from the elite force, supported by the army and police, had begun the assault on central Ramadi at dawn and were advancing towards the government complex."The city will be cleared in the coming 72 hours.
Mr Numani added that the counter-terrorism forces had not faced strong resistance, "only snipers and suicide bombers, and this is a tactic we expected".
Sources in the Iraqi military's Anbar Operations Command told the BBC that engineers had built temporary bridges over the River Euphrates, which flows along the north and west of the city centre. This had enabled troops to enter directly the al-Haouz district, south-west of the government complex.
By Tuesday afternoon, government forces had retaken the al-Thubat and al-Aramil districts, and entered nearby al-Malaab and Bakir, the sources said.
Iraqi intelligence estimates that between 250 and 300 militants are inside Ramadi.
The US military says they have developed a strong defensive system, including using improvised explosive devices (IEDs) to create minefields.
On Monday, the defence ministry warned that the jihadists had prevented civilians leaving since leaflets warning of an assault were dropped over the city last month.
"They plan to use them as human shields," spokesman Naseer Nuri told the Reuters news agency, without indicating the number of civilians who were at risk.
Sources inside Ramadi told the BBC on Tuesday that IS militants had also carried out a campaign of raids and mass arrests of residents in districts still under their control, in an attempt to prevent an uprising in support of the government offensive.
