The head of Egypt's environmental agency, Mohammed Sayyed Khalil, said Cairo wanted written proof that the decommissioned aircraft carrier was not carrying hazardous waste in violation of the Basel Convention banning such trade.

"We have decided to prohibit the Clemenceau from entering Egypt's territorial waters," he said.

In Paris, the defence ministry denied that the warship, which is being towed under French navy escort, had been officially refused access by Egypt, but acknowledged that it had been asked for more information.

"We are being asked for extra technical information, which we are in the process of providing," said ministry spokesman Jean-Francois Bureau.

"We have not been notified of a refusal decision at this point."

The dispatch of the Clemenceau by the French government to a shipbreaking yard in northwestern India has sparked fierce controversy in both countries, with critics accusing Paris of dumping its toxic waste on the Third World.

Two Greenpeace protestors earlier boarded the ship as it was being towed in international waters, climbing one of its masts to unfurl banners reading "Asbestos carrier: stay out of India".

"We let them board. In no way are they impeding the Clemenceau's journey," said the defence ministry spokesman.

He added that a dozen French sailors had later boarded the warship, which had been carrying neither passengers nor crew, and said checks were under way to establish whether the protestors had broken the law.

Greenpeace has been fighting to block the ship's transfer for months, arguing that Indian shipyard workers will be at risk of asbestos poisoning.

Khalil said that he had met on Thursday with Greenpeace's spokesman in Cairo, Martin Besieux, but that Egypt's decision to block the ship's access was unrelated to the group's campaign.

The French maritime governor for the Mediterranean, Vice-Admiral Jean-Marie Van Huffel, said: "Whoever tries to convince Egypt that the ship is a dangerous object, as far as transiting the Suez Canal is concerned, is lying."

The warship, which took part in the 1991 Gulf War, was taken out of service in 1997 when it was superseded by France's new, nuclear-powered aircraft carrier, the Charles de Gaulle.

The ship left the southern French port of Toulon on December 31 after a long legal battle, and is due in India at the end of February.

According to the French government, the vessel is carrying 45 tonnes of asbestos insulation. According to the firm that helped partially decontaminate it before the trip, the amount is between 500 and 1,000 tonnes.

On Friday, an Indian Supreme Court panel temporarily blocked the ship's entry into Indian waters and said it would make a final recommendation in two weeks once it had obtained more information.

India has "already acknowledged that the arrival of the Clemenceau in India would be a violation of the Basel Convention", Greenpeace said.

"There is more than sufficient evidence to establish that the French government has failed to decontaminate the ship, even to the standards they agreed to, let alone to international standards," it said.

"We simply cannot allow the ship to get any closer to its destination."

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