The Iraqi army has urged people living in the centre of the Islamic State-held city of Ramadi to leave before an operation to retake it is launched.
A security source told the BBC leaflets had been dropped by planes, warning residents the army planned to storm the city within the next 24 hours.
The call, which was also broadcast on state television, told them to use an exit secured by the army to the south.
Ramadi was captured by IS in May in an embarrassing defeat for the Iraqi army.
Last month, the US military said Iraqi troops and pro-government militiamen had essentially encircled the city, located about 90km (55 miles) to the west of Baghdad, and that conditions were set for a final assault.
On Monday, a security source told the BBC that the leaflets dropped over Ramadi had urged civilians living in the city centre to leave because government forces were preparing to storm the city from the south, the west and the north.
They were advised to head to the south-eastern Humayra district, where an exit had been secured, the source said.
"This is the last warning by the security forces to the people inside Ramadi," the source added. "The security forces will storm the city, whether residents are inside it or not."
However, a spokesperson for Ramadi residents called on the government to postpone the offensive.
The spokesperson said thousands of families were being held by IS militants, who had set up checkpoints and threatened to kill anyone who attempted to leave.
The US military believes there are between 600 and 1,000 IS militants in Ramadi.
It says they have developed a strong defensive system in and around the city, including using improvised explosive devices (IEDs) to create minefields.
Earlier this month, Iraqi Kurdish forces backed by US-led coalition air strikes recaptured the north-western town of Sinjar from IS in a major operation.