Riot police attempting to clear protesters from Tokyo's new international airport yesterday stormed the demonstrators' hand-made concrete fortress and ripped down its 60-foot steel tower.

Police arrested at least 10 of the demonstrators, who had barricaded themselves inside the castle-like structure, and then used a crane to haul down the tower that had been erected in the flight path of one of the airport's runways.

Meanwhile, Japanese government sources indicated that it will not be possible to open the airport as scheduled Thursday because of the extensive damage caused to aircraft guidance equipment when the control tower was temporarily occupied by demonstrators Sunday.

An emergency meeting of the Japanese Cabinet was being held early today to decide whether to proceed with opening ceremonies. The new airport had been scheduled to open to commercial traffic.

Government officials said they did not believe it is technically possible to begin operations because of the extensive damage to radio communications systems and to parts of the radar equipment.

Six protesters managed to elude hundreds of police Sunday and stormed into the control tower, where they smashed the sensitive guidance machinery with steel bars before being arrested.

Their intrusion was a severe embarrassment to the government of Prime Minister Takeo Fakuda, who had vowed to override the protests and open the airport, seven years after it was first scheduled to begin service for all international flights to and from Japan.

Last night, police turned their attention to the concrete fortress and steel tower that had been built on private land near the end of one airport runway. It was occupied by about 50 men and women who resisted several police thrusts with large slingshots that fired big stones and steel arrows.

Police finally overcame the defenders with a large-scale tear gas assault and arrested 10 of those inside. Most of the others were rounded up as police searched nearby tunnels. More than 200 persons have been arrested at the airport since the last-ditch demonstrations began on Sunday.

Then, early this morning, police used a large crane to rip down the steel tower that had been erected atop the concrete blockhouse.

The opponents are mostly students who have made the airport a symbol of government authority to be blocked and assaulted. Over the past 10 years, they have joined an angry group of farmers whose land has been seized by the airport authorities and turned groups have used lawsuits and violent into runways. Together, the two demonstrations to delay the airport opening.

The latest techniques of infiltration and destruction involved the airport's underground sewer network. Police said one sewer provided a secret entrance Sunday for the bank of helmeted protesters who took command of the control tower.

Yesterday, the embarrassed police began welding shut about 350 manhole covers that provide access to the sewer system.

An organization calling itself the Fourth International Faction said yesterday that its members hid in one sewer for about 24 hours before emerging to take over the control tower on Sunday.

The most serious damage Sunday was the destruction of a large antenna outside the control tower that kept contact with planes over a large area of the Pacific Ocean off Japan's shores.

The control tower's radar screen also was wrecked, although most of the sophisticated radar equipment was located in another part of the building not seized by the protesters.

Airport officials indicated that it may take as long as one month to restore the control tower to full operations. Double-paneled glass windows were smashed when the protesters stormed inside, and the manufacturer said he could not replace them for several days. The sensitive equipment inside cannot be tested satisfactorily until the new windows are in place.