Fairfax County police said yesterday they are increasingly concerned about a spate of recent robberies in which gunmen have brandished illegal automatic weapons.

Shortly before midnight Friday, a man armed with an Israeli-made Uzi submachine gun forced three employes leaving the Safeway supermarket at 5695 Telegraph Rd. into a meat locker at the rear of the store, according to Lt. George Joca.

The assailant took cash, jewelry and watches from the employes after the store manager said he could not open the main safe, Joca said.

About 2:15 a.m. yesterday, two men, armed with what appeared to be a World War II German submachine gun, attempted to rob the Crown service station at 5600 Franconia Rd., Joca said. Joca said attendant Bhagwan Samotra told the men he did not know how to open the station's safe. The assailants took a small amount of pocket change from Samotra and fled.

Police yesterday said they had no evidence linking the two incidents.

On Tuesday night, two men in a pickup truck were chased by police after robbing a 7-Eleven store at 7330 Richmond Hwy. The men, who were still at large yesterday, later fled on foot, but they left an Uzi in the truck.

"I don't know if it's a fad or what," Joca said. "To me and every other officer out there, it is distressing because these things have such firepower. If these guns are out there, it increases the possibility of an armed confrontation, and generally in an armed confrontation the person with the most firepower wins.

"The weapons are apparently more available, and the opportunity is there for an individual who is intent on committing a crime," Joca said.

Automatic guns are legal only if registered as antiques with the U.S. Bureau of Alcohol, Tobacco and Firearms, Joca said. They must be inoperable. Uzi weapons can be purchased legally in semiautomatic form. Some Uzis are later illegally converted to automatic weapons, and some automatic Uzis are smuggled from abroad, police said.