Chanting, shouting, and sweltering in the heat, about 3,000 demonstrators marched through downtown Washington yesterday in the city's second African Liberation Day in a week.

Yesterday's marchers included about equal numbers of college-age blacks and whites plus a small contingent of anti-shah Iranians. Their main appeals were for an end to United States diplomatic ties with South Africa and support for the Wilmington 10, a group convicted of a fire-bombing in North Carolina, whose supporters say are unjustly imprisoned.

Last Saturday a rival group, called the All African People's Revolutionary Party, staged a similar march, led by Stokely Carmichael. It also attracted about 3,000 marchers, including some supporters of the Palestine Liberation Organization and the Irish Republic Army.

The two Liberation Day groups have been feuding since 1974.

Nelson Johnson, chairman of the National Coalition to Support African Liberation Day, the sponsor of yesterday's march, said his group is concerned about "the day to day struggles in this country" well as issues in Africa.

Last week a spokesman for Carmichael's group said it believed that American blacks should "return to their homeland (Africa)" and concentrate on issues there.

Johnson said the largest group of demonstrators yesterday came from New York City, but he said busloads also came from Baltimore, Boston, Pittsburgh, and Detroit.

The temperature, according to the Westher Service, was 87 degrees, the hottest this month. When the marchers reached Pennsylvania Avenue in front of the White House, many of them pressed close to the fence, where it was shady.

Organizers on a sound-track shouted "Carter is a double-talking hypocrite of the worst kind . . ." "Jimmy Carter, you damn peanut farmer," and "Carter, Carter, Cut the Jive, Cut the Ties to Apartheid."

The group then marched back to Meridian Hill Park to listen to speeches.

In mid-morning about 500 demonstrators from the Slovak World Congress marched in front of the White House with signs denouncing Communist rule in Eastern Europe, according to the D.C. mayor's command center.

Just before the African Liberation Day marchers arrived, about 30 pickets demonstrated in the same place against British rule in Northern Ireland.

Meanwhile, in Chinatown, the command center said, about 500 supporters of National Chinese government on Taiwan staged a parade with a paper dragon to mark the inauguration of Chiang Ching-Kue as the Nationalists' new president.