Anti-aircraft guns lit-up the skies over Baghdad early today and at least one fire broke out after President Clinton said he had ordered a "strong, sustained" series of air strikes on Iraq.
The sound of the gunfire thundered around the Baghdad Ministry of Culture and Information offices where western journalists are based shortly after air raid sirens wailed over the Iraqi capital.
A CNN live broadcast from Baghdad showed the orange glow of a fire with smoke billowing.
Sporadic bursts of fire continued more than 90 minutes after the first shots were fired. The firing was at times intense, illuminating Baghdad's night sky.
The thuds of distant explosions were also heard but it was not clear if they were from incoming or outgoing firing.
Iraq radio played patriotic music.
"I have ordered a strong, sustained series of air strikes against Iraq," Mr Clinton said in a televised address from the Oval Office.
US officials said more than 200 aircraft and 20 warships, including 15 B-52 bombers, were deployed in the Gulf region carrying more than 400 cruise missiles and other bombs.
Western defence sources in Kuwait, where US and British warplanes are deployed, said the first waves of strikes were being carried out by B-52 heavy bombers and cruise missiles from warships.
President Saddam Hussein on Wednesday put his country on a war footing to confront the threat of "foreign aggression" prompted by a crisis over UN weapons inspections. Mr Saddam invoked the memory of Iraq's 1991 "Mother of all Battles" against US-led forces and appointed four regional commanders to face any foreign aggression.
Mr Saddam's move came just hours after UN arms inspectors left the country, accusing Iraq of refusing to co-operate.
A defiant statement issued after the Iraqi leader chaired a joint meeting of the Revolutionary Command Council and ruling Ba'ath Party urged ordinary Iraqis to defy looming Western strikes which it said were aimed at bringing Iraq to its knees.
"We call on you Iraqis, women and men, relying on God to throw out their dreams and their failed visions, and prove ... that they will fail as they have failed during the Mother of Battles," said the statement.
"They have been planning for a long time to commit a new aggression against you ... thinking, may God forbid, that they can achieve their goals that all the Arab nation should kneel under their feet," said the statement.
The inspectors, who have worked for seven years to scrap Iraq's banned weapons of mass destruction, evacuated their Baghdad base early on Wednesday and drove to an airport outside Baghdad where they boarded a flight to Bahrain.
Fifty-two United Nations humanitarian staff and dependents also left Baghdad but a UN spokesman said most relief workers would remain in the Iraqi capital for the time being.
He said 143 staff, who oversee distribution of food and medicines in sanctions-hit Iraq, would camp out in the same UN base abandoned by the weapons inspectors hours earlier.
Ordinary Iraqis, wearied by eight years of economic sanctions imposed for Iraq's 1990 invasion of Kuwait and accustomed to repeated showdowns with the United States, said they had little to fear from the latest crisis.
"We are not frightened any more," said one Baghdad trader. "Whatever happens, we are not going to lose anything."
Baghdad's official radio and television reported that Mr Saddam and his top aides had divided the country into four regional commands to confront air strikes.
AFP adds:
A British intelligence report claimed weapons of mass destruction are being stored at the headquarters of Iraq's Ba'ath Party which a UN inspection team was not allowed to visit last week.
The declassified report, released by the British prime minister's office late yesterday, suggested the Baghdad building was being used as a munitions dump.
The report stated that late last year Iraqi authorities "moved sensitive military material by night to a large shed within the compound" of the Ba'ath party offices.
The site was guarded by interior security ministry troops who guard other sensitive sites and prisons, it added.
The intelligence document said the weapons were locked in a cellar below a shed behind a thick steel door.
One source quoted said they were "hidden in a shed made of bricks and with a flat roof".
"The WMD (weapons of mass destruction) material was kept in a cellar below the shed ... A thick steel door (3 x 3 metres) in the floor of the shed led to the cellar.
"The WMD equipment was kept in large wooden boxes, about two metres by two metres by 1.5 metres. The boxes were locked with expensive foreign-made locks sealed with red wax and had something written in a foreign language on them.
"The source thought this language was English and believed that there may have been around 10 boxes in total ..."
Downing Street said the document was used by UN weapons inspection chief Mr Richard Butler to try to inspect the site.