More than 100 Dupont Circle area residents met with D.C. police officials last night to express concern about a series of 30 unsolved armed robberies there in the last two months, all apparently committed by the same man.

Police said they have good descriptions of the robber and some suspects in mind but need the help of circle-area residents to catch him.

"We believe this individual lives in this neighborhood," Capt. Joseph Maddox told the overflow audience in the community room at 3rd District headquarters.

"He has a good observation post in the area. This man seems to know when people come and go in the neighborhood."

The robber has threatened several of his victims, police said, but has not hurt anyone.

Several of those who were robbed attended last night's meeting and said a police sketch of a suspect drawn from descriptions they gave a police artist closely resembled the gunman.

The first of the 30 robberies occurred Dec. 1 at 18th and Swann streets NW, and the most recent on Jan. 27 at 17th and T streets NW, police said. The robber has struck at different hours, from early in the morning to late at night. He wore some of the same items of clothing during most of his robberies--often a blue jacket or a rust-colored ski jacket--and on most occasions used a blue-steel handgun.

"He's very calm and cool," Maddox said.

One of those approached by the robber, accountant Bernard Fisken, said he was getting out of his car in an alley behind his office near 18th and T streets at 5:40 a.m. on Jan. 24 when a young man approached him. Fisken, a former military police officer, said, "I yelled at him, 'No,' because I knew what was happening. He took out a black gun and pointed it at me, and then he said, 'Give me your wallet.' I said, 'I don't have a wallet.'

"Then, like a crazy fool, I lunged at the gun, and yelled, 'Police, police.' I don't like people doing that."

He phoned 911, the police emergency number, and an officer arrived within seconds, Fisken said. But the problems started later, when he was not called by detectives from the police department's armed robbery squad for a followup investigation, Fisken said, and he failed in three telephone calls over the next eight days to reach an investigator.

Some other victims or people who witnessed some of the robberies were also critical, saying that in many instances robbery investigators failed to contact them, or that police were slow to respond to emergency calls.

The robbery squad's Lt. James Botler said the department has assembled a team of detectives and plainclothes officers to catch the suspect.