Baghdad's international airport is also to be shut down for 48 hours.
Iyad Allawi announced the closures during a news conference on Monday where he also gave the authority to US-led forces to storm Falluja.
He said the curfew in Falluja as well as Ramadi would start at 6pm (1500 GMT), under emergency laws he activated on Sunday.
"The measures I will announce now will be implemented after iftar [meal to break the Ramadan fast] at six o'clock, God willing," he said.
Under the emergency measures, Allawi said roads and government institutions in the cities of Falluja and Ramadi would be closed. All weapons would also be banned, he said.
"Once again, we have seen more criminal acts committed by these terrorists who continue to use Falluja as a base for their operations. We have no other option but to take the necessary measures to protect Iraqi people from these killers and liberate Falluja," he said.
US-led troops have already
launched assaults on the city
Allawi said earlier the emergency law was intended to send a serious message about Iraq's commitment to crucial national elections in January.
"We want to secure the country so elections can be done in a peaceful way and the Iraqi people can participate in the elections freely, without the intimidation by terrorists," Allawi said on Sunday.