D.C. police said they are stepping up patrols to combat a recent increase in armed robberies in the Dupont Circle area and attempting to determine if the crimes are linked to this week's slaying of a popular waiter in the neighborhood.

Larry McCoy, commander of the 3rd Police District, deployed canine units, bike patrols and mounted officers to the area after the shooting of waiter Adrien D. Alstad, 55, who was killed as he walked home from work early Monday in the 1800 block of R Street NW.

There have been no arrests in the killing. But police did arrest a suspect yesterday in an attempted robbery that took place in the area less than 24 hours after Alstad's death. They said they had not linked that crime to the slaying.

McCoy said that the robberies are probably the work of a number of criminals, not a single set of assailants. Since January, he said, police have arrested 105 people suspected of being street robbers operating in the Dupont Circle and Logan Circle areas.

"Every kind of thief has their own method of operation," McCoy said. "They're on bicycles sometimes, or they'll approach on foot, or sometimes in a car. . . . There's a lot of variation."

Alstad was accosted about 2:20 a.m. Monday shortly after leaving Annie's Paramount Steak House, a nearby restaurant. He was shot once in the chest. Moments before, witnesses had heard him declare, "I don't have any money."

Another attempted robbery took place about 12:15 a.m. yesterday at 19th and S streets NW, police said. The victim escaped unharmed and did not surrender any money. The assailant got into a white Buick driven by another man and rode off, police said. The victim flagged down an officer, who was in the neighborhood because of the increased law enforcement presence, and a pursuit began.

It ended near St. Elizabeths Hospital in Southeast Washington. Police arrested Delante Mayo, 18, of Oxon Hill on a charge of assault with intent to rob. The driver of the car escaped.

Alstad's death has put his neighborhood on edge and renewed calls for more police.

McCoy said that a large number of officers are on sick leave for extended amounts of time. He called it an "ongoing problem" but added that officers will be shifted from other details to concentrate on the area.

Robert P. Halligan, the advisory neighborhood commissioner for Dupont Circle and co-chairman of its public safety committee, said that a shortage of officers patrolling the streets has left residents vulnerable.

"They do prey on us," Halligan said. "People think of us as big, fat wallets walking around without guns on us."

That assertion rang true for Jeffrey S. Trabaudo, 34, a software and information technology consultant from Glover Park. Trabaudo said he and his girlfriend were the victims of a recent armed robbery at 21st and R streets NW, three blocks from where Alstad was slain.

Trabaudo recounted yesterday how he and his girlfriend were robbed of a wallet and purse at 11:15 p.m. Aug. 6 by a man who approached them with a gun and said, "Give me all of your money or I'll shoot the [expletive]."

The couple had been in the area for a late-night dessert and were shocked by the brazenness of the attacker. Trabaudo said police responded quickly and apprehended a suspect, who turned out not to be the robber. But he questioned how much follow-up was done.

Trabaudo said that after hearing of Alstad's death, "I said, 'Oh my God, this could be the same guy.' I'm glad that they didn't shoot us."

The mood at Annie's Paramount Steak House, where Alstad worked for 12 years, was somber yesterday as bouquets of flowers arrived and customers expressed shock at the news of the slaying. A flier inside the restaurant announced a candlelight vigil for Alstad last night.

Neil G. Griffin, who owns an advertising company at 17th and R streets NW, had lunch yesterday with his partner at the restaurant.

Griffin said that he and his staff often work late and that Alstad's death and other recent attacks have put him on high alert. "I'm wary because . . . we're here all the time, walking around late at night," Griffin said. "I definitely see myself looking both ways and running to my car. It's definitely a wake-up call."