JOHANNESBURG, AUG. 9 -- Three days of the most severe mass rioting in South Africa for many months has left at least 23 people dead and more than 100 injured in the mixed-race, or Colored, townships of Port Elizabeth, in eastern Cape Province.

According to reports from the area, the rioting was sparked Monday when police fired tear gas into a crowd holding a protest meeting over rent increases. For the first time, the African National Congress has worked with police in a joint effort to end the plundering and looting.

In an attempt to translate into action Monday's ground-breaking agreement with the government to suspend its armed struggle and help reduce the level of violence in the country, ANC leaders today addressed a meeting of about 8,000 people to appeal for calm.

ANC marshals visited townships, talking to groups of rioters and removing barricades. But they were threatened and stoned, and at one point forced to withdraw from the scene of a riot.

A reporter who toured the townships today said she counted 35 shops that had been ransacked and burned. She said many liquor stores had been looted and that drunken gangs were rampaging through the streets torching buildings and breaking into stores.

One of the dead was said to have been a baby, shot in its mother's lap.

The Port Elizabeth rioting adds to the complexity of tensions being raised as the country undergoes a drawn-out transition from the apartheid system of racial separation to what most South Africans now believe will be eventual black majority rule. The spread of fighting between supporters of the ANC and Chief Mangosuthu Buthelezi's Inkatha Movement has claimed another 15 lives in Transvaal province so far this week, and the threat of violence by white extremists continues to grow.

Local observers say a number of issues combined to produce an explosive situation in Port Elizabeth's Colored townships, where unemployment is high. Chief among them is the loss of local support for the Labor Party since the government legalized the ANC last February. The party controls the Colored chamber of parliament in South Africa's racially segregated political system, and this region traditionally has been its stronghold. But popular support has been shifting to the ANC, which is seen as the main champion of black rights.

The Labor Party, which has some legislative and administrative authority over Colored areas, has been blamed for a series of rent increases for state- and municipal-owned houses in the townships.

On Aug. 1, the ANC launched a Program of Action to mobilize support in the Port Elizabeth area. As part of this campaign, a rally was organized in the Colored townships Monday to protest the rent increases. When people did not disperse promptly after the rally, police fired tear gas into the crowd.

According to witnesses, this sparked the rioting. The angry crowd rampaged through the streets, stoning vehicles and setting fire to buildings.

Later, after liquor stores were looted, the rioting became wilder -- and gangs of criminals moved in to begin a systematic ransacking of shops. The rioting was reported to be continuing tonight.