All air traffic over Japan has been paralyzed because an underground communication cable for the Tokyo central air control system was cut, Transport Ministry officials said today.

Police said they suspected radicals, opposed to today's planned opening of the controversial new airport at Narita 40 miles east of Tokyo, were responsible for cutting the cable.

When the Tokyo Civil Aviation Traffic Control Center system stopped working, it became impossible for pilots to communicate with control tower officials. Radar screens also went blank.

The cable was cut only hours before the much-postponed opening of Narita airport following years of bloody clashes between police and demonstrators.

More than 14,000 riot police had guarded the new airport during the night amid fears of a spectacular last-minute attack by violent protesters.

In 1966, when work on Narita began, initial opposition came from residents in the area, particularly farmers who had to sell their land.

Leftist radicals opposed to Japan's conservative government subsequently joined the protest movement and police have blamed them for much of the violence connected with the anti-airport campaign.

An opening scheduled for March 30 had to be cancelled when radicals, making their way through underground pipes, got into the tower and smashed its equipment.

Authorities originally had planned to have an elaborate opening ceremony today, including a speech by Prime Minister Takeo Fukuda. For reasons of security, however, those plans were scrapped and only a modest Shinto ceremony was to have been held.

Narita airport was built to ease congestion at Haneda airport which is much closer to the center of Tokyo. It cost $26 Billion and was finished six years but continuing violence had kept it closed until now.

It is surrounded by two fences, dry moats and is patrolled by police and dogs and amored cars equipped with water cannons.

Yesterday, police found a huge cache of firebombs and chemicals weapons hidden near Narita. The stockpile, police said, contained 277 molotov cocktails, 241 empty beer bottles, 16 cans filled with gasoline and 87 vials of a chemical that affects breathing and could cause death.

Earlier yesterday 2 domestic All-Nippon Airways plane with 319 persons on board, made an emergency landing at Nagoya, after an anonymous caller said a time bomb had been put on the planc.

Nothing was found aboard the Lockheed Tristar, which was on a flight from Tokyo to Fukuoka in southern Japan.

Police said the bomb hoax was probably the work of foes of the Narita airport.