Mayor Marion Barry said yesterday he approves of aggressive methods used by 3rd District police officers to control crime in one of the city's most crime-ridden areas, but later in the day criticized the practice of setting arrest quotas for officers.

Barry said yesterday morning that he and Police Chief Maurice T. Turner Jr. had discussed the police measures, which were detailed in a series of Washington Post articles, and had concluded that there was no indication of any wrongdoing by officers. " . . . There's nothing illegal or wrong going on up there," Barry said.

However, Turner said later that he has begun an investigation into the 3rd District's crime fighting methods. If violations of police regulations are found, Turner said, "we will have to take proper disciplinary action against the people involved."

The Post series has disclosed that one of the commanding officers in the 3rd District, Capt. Michael Canfield, has set minimum arrests quotas for his officers.

The series also described measures the officers take against drug dealers and prostitutes in the area. "I've made getting those people off the streets a priority," Barry said early yesterday, adding that the methods, which include raids of street-corner crowds and setting up roadblocks to discourage prostitutes' potential customers, are popular with residents of the affected neighborhoods.

When asked about the quotas early yesterday, Barry said the issue of arrest quotas was "a real problem," but then added, "Some officers on the police force haven't arrested anyone in a year, I know that. Now, there's no way a policeman could work in the 3rd District for one year and not find one illegal act going on. I've been around there. Something's wrong with that officer if he doesn't see anything going on."

Later in the day, however, the mayor denounced quotas. "I don't support police officers illegally and indiscriminately arresting people. And I won't stand for it," Barry said.

"I will not base my decisions on what I've read in the newspapers. I'm opposed to any wrongdoing on the part of any police officer," Barry said late yesterday. "The chief told me today that he started an investigation. The chief and I are absolutely together on that."

Deputy Chief Rodwell M. Catoe, commander of the 3rd District, said, "I have no comment on those articles at this point. There is no quota system in the 3rd District. If there was one prior to the article there is none now."

Gary Hankins, chairman of the bargaining unit for rank-and-file police officers said he feared that officers portrayed in the series might become scapegoats. However, he praised the articles for portraying "tremendous pressures officers face in trying to clear out an area like 14th and U streets to make it safe for citizens."

City Council member David A. Clarke (D-Ward 1), chairman of the council's judiciary committee, which oversees the police department, said he had asked Turner to begin an investigation but had been told one had already been launched.

"The conduct which has been reported in The Post, if true, is not representative of the department as a whole," Clarke said. "The articles reported that people were arrested who weren't guilty . . . that a captain had a different philosophy than his commanding officer. These are matters I think would bear examining."

Council member H.R. Crawford (D-Ward 7) said, "The series right now is not in the best interest of the city. It's not time for this depressing news."

"The tension in town is already high," Crawford said. "I think we should start talking about some of the positive things that police are doing."