Islamic State militants have made further gains in the Iraqi city of Ramadi, with reports of them taking a key military command centre.

Local officials have said the city is on the verge of falling, with army reinforcements unable to hold ground.

The prime minister called on troops not to abandon their posts, while telling Shia militias to prepare to deploy.

Ramadi is the capital of Iraq's largest province, Anbar, and is just 70 miles (112km) west of Baghdad.

Muhannad Haimour, a spokesman for the provincial governor, told AFP news agency that security forces had abandoned an operations command base on Saturday on the northern bank of the Euphrates.

But he added: "Ramadi has not fallen - there are still people fighting in some neighbourhoods."

A police commander said government forces had redeployed from the city to its outskirts.

In comments broadcast on state TV, Prime Minister Haider al-Abadi ordered Shia militias to prepare to join the fight in the Sunni-majority region, the Associated Press reported.

The militias played a key role in the government's recent recapture of Tikrit from IS, but pulled out of the city following reports of widespread violence and looting.

The loss of Ramadi would represent a very serious setback for the government, and Iraqi officials are alarmed, the BBC's Ahmed Maher reports from Baghdad.

Anbar province covers a vast stretch of the country west from the capital Baghdad to the Syrian border, and contains key roads that link Iraq to both Syria and Jordan.

IS reportedly controls more than half of Anbar's territory.

On Friday, IS took a government compound in Ramadi, raising its black flags, before retreating a day later.

A local official said more than 500 people had been killed in the last two days of fighting in and around Ramadi, including policemen who were trapped after running out of ammunition and civilians caught in the crossfire.

Some 8,000 people have been displaced over the same period, according to the International Organisation for Migration.

BBC