A number of US and UK planes have taken part in an attack on a major Iraqi defence facility in the west of the country.

The operation, which targeted the main air defence command centre for western Iraq, is part of the enforcement of the air-exclusion zones over the country, allied military sources said.

There have been about 30 allied attacks against Iraqi installations this year. However, BBC defence correspondent Andrew Gilligan says Thursday's seems to have been much larger than normal.

The raid comes as President George W Bush steps up his campaign to oust Iraqi leader Saddam Hussein.

He is reported to have spoken by phone on Friday with French President Jacques Chirac, Russian President Vladimir Putin and Chinese President Jiang Zemin, Reuters news agency reports, to persuade them that military action against Iraq is essential.

France, Russia and China are known to be sceptical of the need for military action.

The UK Prime Minister, Tony Blair, has told the BBC that Britain must be prepared to pay a "blood price" to secure its special relationship with the US.

And, Arab foreign ministers warned on Thursday that military action to topple Saddam Hussein would "open the gates of hell" and that no Arab countries would join it.

'No casualties'

British defence sources say about 12 jets dropped bombs on western Iraq.

Bush's diplomatic drive

Friday: To call leaders of Russia, China and France Saturday: Talks with British PM Monday: Meeting with Canadian PM Thursday: Speech at the UN

They say that fighter, tanker and radar support planes brought the total number of aircraft in the raid close to three figures.

However, the Pentagon later played down the size of the operation.

"This idea that it's the largest strike in four years is wrong," said Lieutenant Colonel David Lapan, a Pentagon spokesman, referring to a report in the London-based Daily Telegraph.

Correspondents say there is speculation that the operation could be part of initial preparations and intelligence gathering for a full-scale air offensive against Iraq.

Iraq earlier said warplanes attacked civilian targets in the Rutba district in Anbar province on Thursday, but reported no casualties.

President Bush said earlier this week he will seek congressional approval before going to war.

He is also due to meet the UK prime minister at his Camp David retreat at the weekend, and outline his case to the UN Assembly General next Thursday.

Inspectors

Arab League Secretary-General Amr Moussa told a news conference in Cairo on Thursday that any attack would cause major instability in the region.

Amr Moussa: Iraq must talk with UN

The association of 22 Arab states is hoping to head off an attack by pressing the return of UN weapons inspectors to Iraq.

Iraq has repeatedly said it is prepared to talk to the UN about weapons inspections but insists that their return should be part of a comprehensive settlement to end the sanctions imposed on Baghdad after the Gulf War in 1991.

But the US and Britain say words should be matched with deeds and President Bush says he wants Saddam Hussein deposed from power in Iraq.

Bush administration officials said on Wednesday that Mr Bush was considering a UN Security Council resolution that would set a deadline for weapons inspections to resume.

The resolution could imply military action if Saddam Hussein failed to comply.