Fifteen monkeys seized five years ago by Montgomery County police from a Silver Spring laboratory amid charges of animal cruelty have been shipped to a private Louisiana group by the National Institutes of Health, a move promptly protested by animal welfare activists.

NIH officials said yesterday the animals, which are a subject of litigation and a proposed congressional resolution, were transferred from the NIH animal center in Poolesville to the Delta Regional Primate Center in Covington, La., which receives funds from NIH. The move was in the best interest of the monkeys and in response to the "concerns of some members of the Congress and the public," said Dr. William F. Raub, NIH acting director. He said the monkeys will not be subject to "invasive surgical research procedures" and that efforts will be made to "resocialize" them and put them in breeding groups.

Animal rights activists contend that the monkeys should be sent to a sanctuary where they could live in a more natural environment.

Alex Pacheco of People for the Ethical Treatment of Animals said yesterday that the NIH action contradicts what the agency has been "telling a U.S. court -- that they couldn't transfer the monkeys because the NIH isn't the legal owner . . . . Now, literally under the cover of darkness, they have moved the animals."

NIH spokesman Robert Schreiber said an arrangement was worked out with the Institute of Behavioral Resources Inc., the Silver Spring laboratory of an NIH-funded researcher. Before their September 1981 confiscation by Montgomery County police, the monkeys had been used by the laboratory in research on spinal cord injuries. The conviction of a scientist on a cruelty charge was overturned.

A resolution has been introduced in the House and Senate calling for the release of the monkeys to a private sanctuary outside San Antonio.