The Congressional Black Caucus and Jewish groups attacked President Reagan yesterday for his news conference comments about violence in South Africa and his reasons for not visiting a Nazi concentration camp site on the 40th anniversary of its liberation.

"I was not proud of my president last night," said Black Caucus Chairman Rep. Mickey Leland (D-Tex.), who branded as "racist" Reagan's statement that South African police were confronted with a riot and that both black and white police were involved in the shootings that killed at least 18 blacks in South Africa on Thursday.

"The president has acted as an apologist for apartheid in South Africa to the extent of trying to rationalize what happened on Thursday," Leland said.

The latest violence in South Africa took place in Uitenhage, near Port Elizabeth on the Indian Ocean coast, where police opened fire on about 3,000 blacks going to the funeral of a black activist. The funeral coincided with the 25th anniversary of the Sharpeville massacre, which took the lives of 69 South African blacks.

Police said they fired on the crowd after they were attacked by protesters armed with stones, sticks and fire bombs.

While Reagan noted in his nationally televised news conference Thursday night that the violence came from the police, he said that the other side was engaged in a riot.

"I think, to put it that way, that they were simply killed and that the violence was coming totally from the law-and-order side, ignores the fact that there was rioting going on on behalf of others there," Reagan said.

"It is tragic and we hope this can be corrected," he said. "But I think also it is significant that . . . on the police side . . . that some of those enforcing the law and using the guns were black policemen."

Asked if he believed that the black marchers posed a threat to the police, Reagan said, "No. I say there has been increasing violence and there is an element in South Africa that does not want a peaceful settlement of this, who want a violent settlement, who want trouble in the streets, and this is what is going on. I don't hold with what happened and as I say, all of us find the [racial] system there repugnant . . . . "

Leland called Reagan's comments "racist statements." When asked if he thought Reagan was a racist, Leland replied: "If the shoe fits, wear it."

The Black Caucus attacked Reagan's statement that he had no plans to change his policy of "quiet diplomacy" because of the violence in South Africa.

"I am sick and tired . . . of the selective morality of the Reagan administration," Leland said, noting that the White House supports rebels in Nicaragua but declines to change its policy in South Africa.

Rep. Charles B. Rangel (D-N.Y.) said, "It is clear the president has a double standard when it comes to people of color."

Reagan also triggered a flap when he told reporters that he had no plans during his scheduled trip to Germany in May to visit a Nazi concentration camp site on the 40th anniversary of the liberation of Holocaust victims.

Reagan said his visit should come "almost as a celebration of an end of an era and the coming into what has now been some 40 years of peace for us."

"I called the White House this morning and said the president did himself a disservice," Hyman Bookbinder, Washington representative of the American Jewish Committee, said yesterday. "He misspoke. He left the impression that people ought to forget the Holocaust, and that's wrong and I don't think he means it that way . . . . "

Reagan said at his news conference, "I feel very strongly that this time in commemorating the end of that great war that, instead of reawakening the memories and so forth . . . that maybe we should observe this day as the day when, 40 years ago, peace began and friendship; because we now find ourselves allies and friends of the countries we once fought against."