The Justice Department, reacting to pressure from civil rights leaders, today said it has sent more than 300 federal observers to Mississippi to monitor for voting rights violations in Tuesday's runoff election.

William Bradford Reynolds, head of the department's Civil Rights Division, announced that the observers, including 17 attorneys, will be stationed at polling places in 11 counties where "there is a likelihood of interfering with the rights of minorities to vote."

This means that there will be federal observers at polls in three more counties than during the Aug. 2 primary. But civil rights leaders, who had requested observers in at least 23 counties, complained that the response was inadequate.

"There is a crying need for a greater federal presence to protect the right of blacks to vote and to ensure that black candidates don't have the election taken from them," said Robert Walker, field director for the state NAACP.

The Rev. Jesse L. Jackson, whose Operation PUSH has been conducting a get-out-the-vote drive, charged that the federal observers, most of whom are volunteers from the Office of Personnel Management, had not been trained to detect the nuances of white intimidation in Mississippi and were being deployed poorly.

Jackson wanted the Justice Department to send an additional 300 observers, and noted that the department has rejected 14 redistricting plans that would have gerrymandered black voters.

"We're glad they are coming," Jackson said of the observers. The potential Democratic presidential candidate said in an interview, "They are exposing the problem, but they aren't solving it."

He and other civil rights leaders alleged that dozens of voting rights violations occurred during the primary in areas where there were no federal observers. Other black leaders said that they would like to have observers in every county where there is a black majority and in all areas where black candidates are running against whites.

The majority of observers will be stationed at polls in the heavily black Delta region northwest of here.

Black voters in this flat, rural area are thought to hold the key to Evelyn Gandy's hopes of becoming the first woman to win the Democratic gubernatorial nomination here. Gandy, 62, a former lieutenant governor, narrowly won the Aug. 2 primary, but failed to get the 51 percent majority needed for nomination, which is usually tantamount to election in this state.

Now she is fighting history in her attempt to defeat Attorney General Bill Allain. No primary winner has won a Mississippi gubernatorial runoff since 1963. Political observers see the race as a close one that may be decided by black voters in the Delta, who went heavily for third-place finisher Mike Sturdivant, a wealthy businessman and plantation owner, in the primary.

Black leaders are divided between Gandy and Allain, 55, who is running as a self-styled populist.

Gandy has been attacked for endorsing racial segregation in 1963 and for working as an aide to former senator Theodore Bilbo, an outspoken racist. Late last week, she attacked Allain in radio ads for defending the state against civil rights suits brought by blacks in the '60s and '70s, when he was an assistant state attorney general.

The GOP candidate is Clarksdale planter Leon Bramlett, 59.

The Justice Department said today that 32 federal observers will be stationed at Benton County, 64 in Bolivar, seven in Grenada, 16 in Holmes, 25 in Humphreys, 36 in Jasper, 48 in Lowndes, 33 in Noxubee, 37 in Quitman, 34 in Washington and 16 in Yazoo. One attorney will be stationed in Sunflower County, home of former senator James O. Eastland.

The federal team is headed by Gerald W. Jones, chief of Justice's Voting Rights Division.