About 100 United States and British aircraft took part in an attack on a major Iraqi air defence installation, in the biggest single operation over the country for four years, said media reports today.

Quoting allied military sources, a BBC report said the operation that targetted the main air defence centre for western Iraq is part of the enforcement of the air-exclusion zones over the country.

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

BBC said the president is expected to speak by telephone with key members of the UN Security Council today to persuade them that military action against Iraq is essential.

The attack comes despite a warning from Arab foreign ministers yesterday that military action to topple Saddam would "open the gates of hell" and that no Arab countries would join it.

Meanwhile, an AFP report which quoted the London-based Daily Telegraph said the aim of the operation seemed to be the removal of air defences to allow easy access for special forces helicopters to fly into Iraq via Jordan or Saudi Arabia.

These helicopters are expected to hunt down Scud missiles before a possible war within the next few months.

Twelve warplanes dropped precision guided bombs in the raid, but scores of other support aircraft also took part, said the report, adding that it was the first time a target in western Iraq had been attacked during air patrols of the southern no-fly zone.

No casualties reported

In a statement yesterday, the US military reportedly said that the warplanes bombed "an air defence command and control facility at a military airfield 380km west and slightly south of Baghdad" in response to "recent Iraqi hostile acts".

However, the AFP report said an Iraqi military spokesperson claimed that the warplanes bombed civilian installations southwest of Baghdad, without causing any casualties.

The fighter jets flew back to their bases in Kuwait after coming under Iraqi anti-aircraft missile fire, the spokesman added.

Iraq does not recognise the air exclusion zones over its north and south which Britain and the United States have enforced since the end of the 1991 Gulf War, following failed uprisings in those regions by the country's Shiah and Kurdish minorities.

The zones are not sanctioned by any UN resolution and Iraq says almost 1,500 Iraqis have been killed as a result of the flights since 1991.