Police have linked the mysterious slaying of a Wheaton civic activist June 5 with a shooting in a Chevy Chase neighborhood the same night in which no one was hurt.

Montgomery County police said yesterday the weapon that killed Irene Yaskovich, 53, who was shot while sitting in the dining room of her home at 1817 Arcola Ave. in Wheaton, was also used an hour later to shoot up several street signs and the front of a house in the 7600 block of Rosdhu ct. in Chevy Chase. The two locations are about four miles apart.

The weapon, according to ballistics tests on slugs found at both sites, was a semiautomatic rifle similar to ones used by U.S. troops in Vietnam.

The shots that killed Mrs. Yaskovich, the mother of three children, were fired from a small wooded area behind her home, according to police. She was alone, sitting at her dining room table typing when bullets smashed through the window behind her and one pierced her back.

Fragments of 15 .223-caliber bullets were found near the home.

Yaskovich was known in her neighborhood as an activist who worked with civic associations and other groups and campaigned for such things as more streets lights. Police said they have determined no motive for her slaying and have no suspects.

About an hour after the slaying, several residents of the area around Beach Drive and the Capital Beltway, which is near Rosdhu Ct., reported hearing gunshots and a car speeding away, according to police.

The weapon believed used in both shootings was a Colt AR15 rifle, Colt AR15 carbine or Armalite AR180 rifle. The three, similar in design, are semiautomatic and available commercially.

All three are also similar to the M16 rifle used by the U.S. Army. A principal difference is that, while the M16 can be put on automatic fire, discharging a stream of bullets with one pull of the trigger, the others require one trigger pull to fire each bullet.

The semiautomatic weapons, popular for hunting small game such as squirrels and rabbits, can be fired rapidly although it lacks the automatic feature.

A $1,000 reward is offered under the county police Crime Solvers program for information leading to arrest and indictment of a suspect in the Yaskovich slaying.