A contingent of about 80 D.C. police officers and FBI agents last night sealed off one of the city's most flagrant and deeply entrenched drug markets at Hanover Place NW in the latest attempt to disrupt what officials describe as the center of cocaine trafficking here.

Shortly after 10 p.m., officers roped off virtually all entrances to the one-block area near North Capitol Street and New York Avenue, demanded to see identification papers of anyone they could find -- including residents who were walking by -- and made at least six arrests on drug and weapons charges.

The block, a blighted stretch of boarded-up houses, graffiti-smeared walls, trash-strewn sidewalks and abandoned automobiles, took on the air of an occupied zone as police turned back visitors and told them they could not enter the area without showing proof that they lived there.

The Hanover Place raid -- the third in the last 18 months -- was accomplished swiftly by uniformed officers in patrol cars. But officials offered little comment on the action, citing a scheduled press conference today by Mayor Marion Barry and Police Chief Maurice T. Turner Jr., who plan to visit the site.

"We are here to stay and we are here to clean up Hanover," said Deputy Chief Max Krupo, 1st District commander. "You'll hear it all at the press conference tomorrow. I can't say anymore."

One vice officer who asked not to be named said police would continue their vigil at least until Christmas "and probably through New Year's."

Ten officers remained stationed at entrances to the block late last night, turning away motorists and pedestrians.

Police -- dubbing the raid "Operation Avalanche" -- quickly surrounded about 75 people who were on the streets at the time, lined them up against buildings and checked their names for outstanding arrest warrants.

Officers also stormed six houses, apparently searching for drugs, and stretched yellow tape across streets leading into the neighborhood, preventing anyone from entering.

It was unclear how many of those stopped by police had been engaged in drug sales, although earlier in the evening numerous men bundled in parkas against the cold were seen in the area, beckoning to motorists on North Capitol Street to buy drugs.

One of those detained was D.C. resident Billy Banks, 30, an employe at Walter Reed Army Medical Center, who said he was on his way home from the post office.

"The police came in and said, 'Get up against the wall!' " Banks said. "All they wanted to do was check IDs. I think they were pretty fair. I was the first one to put my hands up, just like on TV."

Greg Hannan, an artist who maintains a studio in the neighborhood, said he was prevented from delivering a load of wood for some carpentry work he was doing there, but he apparently didn't mind the inconvenience.

"This has been a long time coming," Hannan said of the raid. "It's been extremely bad down here for a long time."

Another longtime resident, Michael Robertson, 32, suggested that the police should stay permanently.

"The police did real good last year. They cleaned it up real good," Robertson said. "For six months my kids could play on the street. All of a sudden they [police] slacked off and the dealers came back . . . . I don't let my kid go out."

Bordered by First, O, N and North Capitol streets, Hanover Place is also connected to a number of alleys that provide protection for drug dealers and make continuous police surveillance difficult.

There are few businesses or residents in the area, and drug peddlers also take refuge in a number of vacant houses.

In June 1984, police conducted the first Hanover Place operation -- called Beat It -- in which officers occupied the block for two weeks, checked every car that entered and made 35 arrests on drug charges. The second effort, last December -- called Beat It II -- produced about a dozen arrests in the first few days. The drug peddlers seem to reappear almost as soon as the police leave. The raids follow closely the publicity given to Hanover Place and other major drug markets in the city.

Last night's action came one week after an article appeared in The Washington Post detailing gunfire associated with the drug trade around Hanover Place and the emergence of that market as a possible battleground for rival East Coast drug dealers.