Iraq's armed forces began attack to retake center of Ramadi on Tuesday from Daesh militants who have held the western city since May, a spokesman for the counter-terrorism units, Sabah al-Numani, said.

The operation to recapture Ramadi, 100 km (60 miles) west of Baghdad, began early last month after a months-long effort to cut off supply lines to the city, whose fall to Daesh was a major defeat for Iraq's weak central government.

"Our forces are advancing toward the government complex in the center of Ramadi," Numani said. "The fighting is in the neighborhoods around the complex, with support from the air force," he said and added: "The city will be cleared in the coming 72 hours."

"We went into the centre of Ramadi from several fronts and we began purging residential areas," he added.

Iraqi intelligence estimates the number of Daesh fighters entrenched in the center of Ramadi, capital of Western Anbar province, at between 250 and 300.

Retaking the city would provide a major psychological boost to Iraqi security forces after Daesh seized a third of Iraq, a major OPEC oil producer and U.S ally, last year.