The body of a young woman was found in South Arlington yesterday, the second such body found in the county in 24 hours and the sixth in Northern Virginia this year, police said.

Authorities said the body of Sandra Rene Johnson, 20, was discovered about 5:30 a.m. yesterday inside the Country Club Towers building at 2400 S. Glebe Rd., two blocks from Interstate 395 and less than two miles from a parking garage where the body of Sherry K. Larman, 26, was found about 9:30 a.m. Saturday. Larman was described as a lifelong area resident who was living in Maryland at the time of her death.

Authorities called both deaths suspicious but declined to say whether the two fatalities were related.

"Obviously we don't know yet," Arlington Detective Ken Rosenberg said yesterday. He said police are releasing few details of the incidents because "we don't know what we have yet. It's so early in the investigation."

Police said that autopsies are to be performed tomorrow but that they could give no information about the possible cause of death in either of the cases. Authorities said Johnson lived in the high-rise apartment building where she was found, but they provided no information about where or how her body was discovered.

Larman had been found face down on the top deck of a four-story garage at 901 S. Highland St., near Columbia Pike, dressed only in black underpants.

Falls Church police are still trying to identify a woman whose body was found May 9 in a residential neighborhood. On April 1, Anne Borghesani, 23, was fatally stabbed in the Rosslyn section of Arlington just off the I-66 bicycle trail.

In March, a woman identified by police as a D.C. prostitute was found shot to death in Alexandria, and a similar killing was reported in Fairfax County in February.

Only one confirmed homicide has occurred in Arlington this year. Officials said that two residents died in an apparent murder-suicide in March. Last year one homicide was reported in the county; in 1988 five slayings occurred.

Some residents of Country Club Towers, where Johnson's body was found, said they are increasingly worried about safety.

"It's beginning to get a little frightening," said Nancy J. Smith, who said she learned of Johnson's death about 7:30 yesterday morning when police came to her apartment to ask her if she had heard anything during the night.

Smith said that security is good in the building and that it had been tightened recently in response to news reports about drug sales in the adjacent Nauck neighborhood. Despite the precautionary measures, she said, "It's scary if you live here" and a young woman's body is found.

Neighbor Sherie Klenk said, "I'm just surprised. There's always somebody at the front desk," and strangers are asked to identify themselves. A spokeswoman for the building's management firm said yesterday afternoon police had given her little information and she could not comment on the death of Johnson.

John Robinson, director of the Martin Luther King Community Center a few blocks from Country Club Towers, said he has been warning young women about walking at night in the neighborhood. "You've got to be careful -- young and old," he said.

"The police have been doing a good job," Robinson said, adding that the area around Drew Model School has attracted drug dealers and buyers. The lifelong county resident said he is not surprised at the discovery of two bodies, adding, "I don't like it to happen in Arlington -- or anyplace."