The District has had an unusual series of apparently unrelated homicides this week with five slayings in the last six days -- the latest a young woman found stabbed and strangled yesterday morning near the Southwest waterfront.

All five of the recent slayings remain unsolved, and all were characterized either by extreme brutality or uncommon efficiency. They bring the number of homicides in Washington so far this year to 122.

Police said the latest victim, who has not yet been identified, was found about 5:30 a.m. in the 1400 block of Maine Avenue SW, beneath the 14th Street overpass near the Tidal Basin. Police said the woman, described as in her late teens or early twenties, was probably killed somewhere else and her body left there. An autopsy showed that the woman died of stab wounds in the chest and strangulation, according to a spokesman for the D.C. medical examiner. He declined to release the approximate time of her death.

The recent spate of homicides began last Sunday, when the body of another young woman, 22-year-old Florence Eyssalenne, a paralegal with the firm of Spiegel and McDiarmid, was found with her throat slashed in her Capitol Hill apartment.

Eyssalenne, a 1984 graduate of Harvard, was the third paralegal employed by the firm to be killed since 1981.

Police sources said that yesterday's victim, like Eyssalenne, appeared to have been brutally beaten and possibly sexually assaulted. They said, however, that the two cases do not appear to be related.

Three men also were killed in unrelated incidents this week, and police said that the men were all shot at least once in the head.

On Tuesday, Andre Jackson, an 18-year-old junior and basketball player at Coolidge High School in Northwest, was shot in the head several times as he was leaving his home at 44 Q St. NE to go to class. Police said Jackson's death may have stemmed from his potential testimony in an upcoming, drug-related murder trial.

The next night, two Southeast men were shot and killed. Police said that Zino Bryant, 20, of 1425 Cedar St. SE, was shot in the head while walking in the 400 block of U Street NW by a man who stopped his car, got out and fired several shots.

Also Wednesday night, the body of 44-year-old Nathaniel McNab, who had been shot once in the back of the head, was found in the back seat of a car parked in the 3700 block of Massachusetts Avenue SE.

Police said they believed the shooting of McNab, who lived at 3655 Alabama Ave. SE, was drug-related.

D.C. police officials and investigators yesterday refused to comment publicly on the slayings, saying that they had been ordered not to talk to the media.

The homicide branch declined to research the last time five persons were killed in such a short period, though police said it was probably in early April, when a double homicide was followed within a few days by the slaying of four persons in a Southeast apartment. That case, the largest multiple murder in the District since 1973, is also unsolved.

Police said that no arrests have been made in 40 of the 122 homicides in the District this year.

Police said the unidentified woman found slain yesterday was about 5 feet 4 inches tall, weighed about 105 lbs, had a medium- to dark-brown complexion and short black hair. They said she was wearing maroon pants with maroon, white and pink socks and a long-sleeved light blue shirt with the words "Don't touch the merchandise" written across the front.