Assistant Attorney General William Bradford Reynolds, fresh from touring the Delta and hearing blacks testify about their problems in voting, ordered federal examiners yesterday to report immediately to five Mississippi counties to register voters for the state's Aug. 2 primary.

Reynolds, head of the Justice Department's Civil Rights Division, made the two-day trip with civil rights activist Jesse Jackson, who complained to Reynolds a week ago and asked for help.

"It is clear to me that the ability to register was not as open and accessible as it might be to a number of blacks . . . who have to work during the business hours and don't have the ability to register except in the evening hours or on the weekends," Reynolds said.

"I've heard about discriminatory redistricting. I've heard about access to the circuit clerk being denied. I've heard about intimidation at the ballot box. And I've heard about difficulty with annexation," Reynolds said.

He also said he had received complaints from blacks about county officials who moved polling places out of black neighborhoods and into white ones without informing voters or the Justice Department.

"Any change of a polling place has to be pre-cleared with the Justice Department," he said. "We will respond to that--if it's going on--forcefully and promptly."

Reynolds, who has received intense criticism from civil rights groups because of his positions against affirmative-action quotas and school busing, denied that his trip with Jackson was intended to improve the Reagan administration's image among black voters.

"I have an absolute intolerance for racial discrimination," he said. "I did not go down on this trip with anything that was different from anything I came back with . . . . My job is to enforce these laws the best way I can. There is no new direction in our civil rights enforcement policy."

Reynolds said Justice has begun an investigation into some Mississippi counties' voting practices and said he has put the wheels in motion to send federal observers into Mississippi for the election if they are needed.

Reynolds also said he is naming a special "liaison" in his division's voting rights section to handle complaints about Mississippi.

Federal registrars last visited Mississippi eight years ago.

To sign up voters in the five counties, Reynolds said, a total of 10 federal registrars were scheduled to start work last night in the cities of Belzoni, Greenwood, Canton, Marks and Ruleville from 6 to 9 p.m., today from noon to 9 p.m., Saturday from 8 a.m. to 6 p.m. and Sunday from noon to 6 p.m.

The Voting Rights Act authorizes Justice to send federal registrars to counties after a determination that there may be racial discrimination in local registration rules. Under the law, the federal registrars can enroll voters up to 45 days before the election. Reynolds said he was forced to move quickly in this case because the 45-day deadline occurs Sunday.

Under state law, voters can register until July 2, 30 days before the primary.

Reynolds said he has not decided yet whether Justice will file a lawsuit to force changes in county voter registration practices. "What I saw and heard suggests to me that there are some problems . . . that are going to require a careful examination."