IN THE TOWN of Kerala in eastern Afghanistan last April 20, survivors now in Pakistan have told The Christian Science Monitor and Newsweek, some 20 Soviet advisers led Afghan troops in the massacre of an estimated 1,000 or more unarmed people who had been rounded up for supporting the anti-government Moslem resistance. "They forced all the men to line up in crouching positions in the field just outside the town and then opened up with their machine guns from behind," one witness recalled. The command to shoot was given by a dar-blond, green-eyed Russian officer speaking Pushtu. The bodies were bulldozed.

The slaughter of defenseless civilians accused of providing support to national forces resisting foreign intervention is, of course, a familiar 20-century story. Yet there is a special quality to the brutiality reported at Kerala. It does not seem to have been the work of an errant soldier acting in violation of the established policy and his government. The circumstances in Kerala suggest at the least a degree of official complicity on the part of the Soviet command, and at the most a Soviet policy decision to quell resistance of any cost.

Among some people there may be a certain tendency to shrug off the new atrocity tales -- on grounds that everyone already knows how brutal the Russians are generally and how ruthless they hav been in Afghanistan. But literally and figuratively, that allows Moscow to get away with murder, past and future. What is at issue, after all, is the murder of more than 1,000 unarmed civilians at one time. The current Soviet line on Afghanistan is that the United States should write the place off and return to the pursuit of detente. But is is Soviet actions, which cannot be concealed from outside scrutiny, that undercut the Soviet line.

Moscow reacted with uncommon speed to the new accounts, terming them "monstrous misinformation." Obviously it senses that the Kerala reports can produce a firestorm of propaganda and criticism. (Keep in mind -- the Kremlin surely does -- that the Soviet Union is still in the dock for its massacre of captive Polish officers at Katyn in 1940.) In fact, if Mocow is serious about its denial, it will allow impartial investigators to go promptly to the scene. American satellite cameras should, meanwhile, keep watch.