A squad of Republican poll watchers dressed in private security guard uniforms, some carrying sticks and chemical spray dispensers on their belts, challenged scores of voters in black precincts here today, triggering a rash of complaints to city and state election officials.

Assistant Attorney General Jack Schwartz, head of a special election monitoring task force, said state and city investigators said a "floating team" of about 12 uniformed men roamed through several precincts in predominantly Democratic and black areas of west Baltimore, challenging voters as they stood in line. State Republican officials also acknowledged dispatching the uniformed watchers.

At least three of the men wore chemical spray dispensers and short leatherbound "slapsticks," Schwartz said. He said the men, all wearing the uniform of a private security company in Howard County, violated election rules by speaking directly to voters, asking them if they were registered and otherwise entitled to vote.

City police were alerted to stop the watchers from engaging in improper activity, he said, and the group disappeared from the streets in the afternoon.

Maryland Attorney General Stephen H. Sachs, a Democrat, said the use of uniformed patrol watchers "represents a radical departure from a bipartisan tradition in Maryland . . . . To come in here with uniformed heavies can have no other effect than to intimidate. . . . "

Robert Owen, director of ballot security for the Maryland Reagan-Bush campaign, acknowledged that "about 10" men in uniform were sent by the state Republican Party into low-GOP-turnout precincts.

He said officials stopped the watchers at midday and told them to remove their uniforms. Asked why they were wearing uniforms, Owen said, "Just to show the flag."

For his part, GOP leader Owen said he filed about 50 complaints that some of his watchers were ejected from the polls and harassed by Democratic officials.