The head of Egypt's environmental agency, Mohammed Sayyed Khalil, said Cairo was demanding a document to prove that the ship 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.

The decision was taken before two Greenpeace activists boarded the vessel early Thursday to protest its transfer under tow to India, he said.

Greenpeace has warned that workers in India would be at risk of asbestos poisoning.

Its campaigners used a motorised dinghy to approach the ship, which had nobody on board and was escorted by a French naval vessel, in international waters off the Egyptian coast, the French defence ministry said.

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

The activists climbed one of the ship's masts with banners reading "Asbestos carrier: stay out of India", Greenpeace said in a statement.

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

The Clemenceau, which took part in the 1991 Gulf War, was taken out of service in 1997 when it was superseded by France's new, nuclear-powered aircraft carrier, the Charles de Gaulle.

It left the Mediterranean port of Toulon on December 31 after a long legal battle, and is due in India at the end of February.

"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," Greenpeace said.

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

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.