Since the imposition of martial law in Poland, public attention has focused on the fate of the thousands of Solidarity activists interned in camps around the country. But detention without trial is only one of a range of repressive techniques now being employed by the Polish military authorities in reasserting their control.

The number of people being held has been disputed. But, now that more evidence of where they are being held has come to light, Western observers here are more inclined to accept the government's official figure of 5,000.

An order of the Justice Ministry dated Dec. 13, the day of the crackdown, established 47 internment camps scattered around Poland's 49 regions. It appears that each contains between 60 and 350 prisoners.

Many more Solidarity sympathizers have been fired from their jobs, detained for brief periods, persuaded to sign "loyalty oaths," forced to leave the union or otherwise harassed for their beliefs. According to official statistics given to the national legislature this week, more than 30,000 people have been summoned before special courts for offenses under martial law.

The deputy minister of interior said that, in addition to 5,067 people detained as of Jan. 7, nearly 3,000 others had been arrested. The legal distinction between internment and arrest is that those who are interned have not been charged with any crimes.

Perhaps the most common technique used by the police is that of brief interrogation. The "suspect" is picked virtually at random, questioned for several hours, and then--once he has been thoroughly scared--released with a severe warning.

An account said to be that of one such suspect was recently published by an underground Solidarity bulletin. The student--we shall call him Piotr--said that he had been arrested and released for no apparent reason.

His ordeal, according to the Solidarity account, began at 6 p.m. on a weekday evening when two men in plainclothes showed up at his apartment. They flashed their identity cards but not long enough for him to read their names. They had come, they said, for Piotr's brother-in-law, but they decided to take Piotr to the police station as well.

At militia headquarters on Rakowiecka Street, Piotr was led into a typically furnished office. The blinds were down, and several other men in plainclothes were standing around the room. Before the interrogation, Piotr was thoroughly searched --right down to his shoes and socks.

The questioning began with his alleged presence in the public gallery at a trial of members of the rightist dissident group, Confederation for an Independent Poland (KPN). The interrogators asked him repeatedly what he was doing at the trial, where he got badges and leaflets from the organization and which students distributed uncensored literature in his dormitory.

"When I told them that I had never been present at the trial, they accused me of lying," Piotr said. "They also accused me of belonging to the Independent Students' Union, which I also denied."

The first part of the interrogation lasted two hours, and various techniques were used. One member of the Polish secret police kept issuing threats, while the others spoke to him politely.

The second police officer suggested that he should take advantage of the amnesty offered by the military government for all political crimes committed before the imposition of martial law--provided that an investigation had not already begun.

"If you don't confess under the amnesty, we'll have to send you to . . . " added the second interrogator, not specifying where.

Bewildered over what he was supposed to have done wrong, Piotr said he had nothing to confess. The police then produced a white plastic rope and ordered him to take off his shoes. Three witnesses were brought in.

Two of the witnesses, both uniformed policemen, said they had been present at the KPN trial and had noticed Piotr among the spectators. The third witness was a civilian who claimed that he was a former dissident who had seen the error of his ways and decided to cooperate with the authorities. He, too, claimed to have seen Piotr at the trial.

Throughout the interrogation, the civilian stared at Piotr. When Piotr stared back, the man rushed up to him, kicked him and ordered him to remain standing. It was the only time physical violence was actually used.

The interrogators adopted another tactic. They said they were sorry for him as he was so young and so easy to lead astray. They gave him several uncensored leaflets to look at and asked if he had ever read them before. When he told them he had not, they threatened to use the leaflets as evidence since they now bore Piotr's fingerprints.

Finally, he was handed a form saying that he promised to stop his antistate activities and "observe current laws and regulations." Piotr refused to sign the statement on the ground that it amounted to an admission that he had broken the law in the past. He was told to "think it over" and return the next day at 3 p.m.

The following day, Piotr was led to another interrogation room. Once again he refused to sign the "loyalty oath." The interrogator started shouting.

"I'll see to it that you're thrown out of your polytechnic," he said. "The government does not need engineers that don't respect it. Why should we invest in the likes of you?"

The interrogator told Piotr that he could expect to be drafted into the Army and, if he broke any of the martial-law regulations in the meantime, he would be in deep trouble. He was given another statement to sign promising to return to his hometown and saying that he was aware of the legal consequences of his activities. Someone took his identity card away, and he was kept waiting for another hour before it was returned.

The parting word was given by a member of the secret police who showed him to the door: "Whatever you say or don't say doesn't matter anyway. People like you belong to the dregs of society. It's not worth paying for your upkeep."