Iraqi military planes dropped leaflets on Sunday on Ramadi, asking residents to leave within 72 hours the western city, which is under the control of Islamic State militants, an army spokesman said.
"It is an indication that a major military operation to retake the city center will start soon," one officer said on condition of anonymity.
The leaflets indicated safe routes for civilians to exit the city and asked them to carry proper identification documents, joint operations spokesman Brigadier General Yahya Rasool told Reuters by phone. "All security forces were instructed on how to deal with civilian approaching them."
Last week Iraqi security forces said they had made advances on two fronts in Ramadi, clearing Islamic State militants from a military command base and the sprawling neighborhood of al-Taamim on the western rim of the city that they captured in May.
Iraqi intelligence estimates the number of Islamic State fighters that are entrenched in the centre of Ramadi, capital of the Sunni Anbar province, at between 250 and 300.