MANDALAY, MYANMAR -- With a massive show of force and a series of raids on politically active monasteries here, Myanmar's military junta appears to have crushed, at least for now, a budding opposition movement by the country's Buddhist monks.

Angered by a boycott in which monks in this central Burmese city refused to minister to soldiers, the military has raided more than a dozen monasteries since Monday and seized a variety of prohibited items ranging from political tracts to slingshots. Authorities of Myanmar, formerly Burma, have not reported any arrests, but political sources said at least 40 monks have been detained and that others are in hiding.

Now, this former Burmese capital has the look of an occupied city. But instead of foreign invaders, like the British who captured Mandalay in 1885, today's occupiers are members of Myanmar's own Tatmadaw, as the army is called. Helmeted troops armed with automatic weapons and grenade launchers patrol neighborhoods on foot and in trucks, man barbed-wire roadblocks on downtown streets and guard key intersections and installations.

As the 11 p.m. curfew approached one night this week, soldiers cradling German-designed G3 assault rifles set out in single file through a residential neighborhood like a combat patrol through enemy territory.

Even before the raids, troops had taken over several Buddhist pagodas in the southwestern part of the city near the more activist monasteries, turning the shrines into garrisons and staging areas. Residents said some had been brought in from areas where the army is fighting ethnic insurgencies.

On the day the raids started, a half-dozen troop trucks were parked in the interior courtyard of a military-held pagoda listed in guidebooks as a tourist attraction, and a room featuring a showcase of bronze Buddha statues had been turned into a command post.

Barefoot officers, observing a rule against footwear in such holy places, sat on the floor tapping out reports on a typewriter and shuffling through sheaves of papers, while others worked a telephone and radios. "We've been having some problems with the monks, but it's calm now," said a captain. "The monks are getting too much involved in politics."

The latest trouble here began Aug. 8, on the second anniversary of a 1988 military massacre in the capital, Yangon, in which soldiers killed at least 1,000 unarmed demonstrators protesting the imposition of martial law. About 300 monks and students who marched to mark the anniversary were met by troops who tried to arrest a student leader and eventually opened fire on the demonstrators, killing two monks and two students, opposition activists said. The government denies that there were any deaths.

In late August, more than 3,000 monks from at least three Buddhist dissident organizations began refusing to accept alms from soldiers or officiate at ceremonies for them. The boycott was joined by many of the estimated 70,000 monks in Mandalay, considered Myanmar's religious capital, and this month began spreading to other cities, including Yangon.

Apparently alarmed by the boycott's effect on military morale in a country where more than 80 percent of the population adheres to a strict brand of Buddhism, the junta last week banned the three monastic sects and ordered the monks to end the boycott. At the same time, the military stepped up efforts to appease senior Buddhist abbots by staging televised appearances in which the generals knelt before them, as is traditional for the faithful here.

However, critics said the efforts may have backfired somewhat when the generals also were filmed giving the abbots such nontraditional offerings as color television sets and bottles of imported soft drinks.

The junta, known as the State Law and Order Restoration Council and headed by Gen. Saw Maung, sent troops into Mandalay's sprawling Phayagyi monastery as a first step, raiding 133 monastic buildings within the huge compound Monday. According to government radio, the troops seized two mimeograph machines, stamps, ink pads, staplers and various "illegal" publications, flags and other political paraphernalia, including badges of the opposition National League for Democracy. Despite the league's overwhelming victory in a national election in May, the ruling council so far has refused to transfer power to it or allow the convening of a new parliament.

In an apparent effort to discredit the monks, official media have also reported the seizure at raided monasteries of jewelry, stacks of money, drugs, playing cards, wigs and civilian clothing, including women's brassieres. Photos have been published of seized weapons such as slingshots and homemade darts.

At least two teaching monasteries in Yangon also have been raided in recent days, residents said. Coinciding with the raids, security forces have closed a number of National League for Democracy offices in Yangon and other cities and detained several party leaders.

Faced with the strong-arm tactics, dozens of high-ranking monks from Yangon and the Mandalay area have publicly withdrawn support for the boycott. Dissidents and foreign diplomats say there appears to be little chance that the monkhood, a potentially powerful organization, can pick up the pieces of the political opposition and lead a new upheaval against the restoration council, which has ruled since September 1988.

However, resentment of the military rule remains intense. "We need foreign countries to help us. That's the only way," said a high-ranking 69-year-old abbot.