Iraqi television says authorities will impose a travel ban out of Baghdad from 6 p.m. to 6 a.m. (3 p.m. to 3 a.m. British time) beginning tonight as US forces close in on the Iraqi capital.
"It has been decided that there will be a ban on the movement of vehicles and people from and into the capital Baghdad between 6 p.m. and 6 a.m. until further notice," an announcer said on state television on Saturday.
Until the announcement of the ban, there had been a fair number of people and cars moving out of Baghdad, even at night.
Worn out by days of bombing, thousands of Iraqi civilians fled Baghdad on Saturday, trudging to relative safety behind U.S. military lines or else heading north away from the relentless American advance.
Men, women and children walked for hours through the fierce heat of an early summer's day, carrying at most the odd plastic bag, blankets or tin kettle between them.
Just before the announcement of the travel ban, Reuters correspondents in the centre of Baghdad heard heavy artillery echoing from the western outskirts of the city.
"There was lots of rumbling. We heard it echoing across the capital," correspondent Samia Nakhoul said.
The Pentagon responded to the announcement by saying it would have no impact on the activities of US-led military forces attacking the city.
"We will go wherever and whenever we want," a Pentagon spokesman told journalists. "It will have no impact on coalition military operations."
US forces captured Baghdad airport on Friday -- their biggest prize yet in the war to oust President Saddam Hussein. They have since pummelled Iraqi positions around the southern outskirts of the city with artillery, missiles and bombs.
The commander of the US air war against Iraq said attack jets, air controllers and unmanned spy planes were on 24-hour alert over Baghdad ahead of a ground war in the city.
Late on Saturday, a bomb hit central Baghdad about 100 metres (yards) from the Palestine Hotel where many journalists covering the war in Iraq are staying and where Iraq's information ministry briefings have been held.