Polish riot police and Solidarity supporters clashed in the Krakow suburb of Nowa Huta for the third consecutive day following memorial services tonight for a young demonstrator killed by a secret policeman.

The disturbances erupted outside a church at 7 p.m. when riot police, using water cannons and tear gas, attacked a crowd of several hundred people who had been chanting Solidarity slogans.

There were unconfirmed reports of attempted strikes at the giant Lenin steel mill in Nowa Huta, where workers have been at the center of the recent disturbances. Leaflets circulating in several cities including Warsaw have called for further protests next week against the Polish parliament's action last week dissolving all existing trade unions, including Solidarity.

It is generally believed that strikes, particularly at large factories, pose much more of a threat to the martial-law authorities than uncoordinated demonstrations, which can be suppressed relatively easily.

Wednesday's shooting of 20-year-old Bogdan Wlosik, a worker at the Nowa Huta steel mill, has fueled an angry mood among workers there just as tensions were subsiding following the collapse of a two-day strike at the shipyards along the Baltic coast. This morning, Cardinal Franciszek Macharski, Pope John Paul II's successor as archbishop of Krakow, prayed for reconciliation at a tomb built in honor of Wlosik.

Sharply contradictory accounts are circulating about the circumstances of Wlosik's death, although both sides agree that he was shot in a park not far from the Nowa Huta church after a march by workers from the steel mill to the church had been attacked by police.

According to the official version, the plainclothed policeman involved in the incident was "brutally attacked" by the crowd and pushed to the ground. Acting in self-defense, according to officials, he fired a warning shot and then another shot that fatally wounded Wlosik.

Independent witnesses, including Western television crews, say the incident began when Wlosik pointed to the plainclothed man and yelled to fellow demonstrators that he recognized him as an agent for the security police. The policeman, who has not been identified, pulled a pistol from his coat, according to these witnesses, and, while running away, fired two shots at Wlosik from a distance of about 10 yards. He jumped into a passing police car and was driven away.

These witnesses dispute the official claim that a warning shot was fired or that the plainclothed man was pushed to the ground.

Before today's clashes, the area in front of the church -- which was consecrated in 1977 by Cardinal Karol Wojtyla before he was elevated to the papacy -- was sealed off entirely by police.

Independent reports from Nowa Huta earlier today said that the two days of street fighting had left extensive property damage. Numerous benches and rubbish cans reportedly had been overturned to make barricades, some of which were set on fire by demonstrators.

A statue of Lenin was reported to have twice been knocked off its pedestal in front of the Nowa Huta steelworks. Workers were seen repairing the monument Thursday and today.

Like other workers in Poland, the steelworkers appear to be boycotting official attempts to persuade them to set up new unions in place of Solidarity. So far, less than 100 of the work force of 40,000 at the steel mill, the country's largest factory, have signed up for the new union, sources said.