At least 11 more people were reported killed today in political violence here as the formerly tranquil black and mixed-race townships of the Cape Town area erupted for the second straight day.

The death toll during two days of mass protests against the white-minority government and harsh police measures now is at least 16. Three other deaths were reported in separate incidents elsewhere in South Africa in a fresh round of the political violence that has claimed more than 650 lives in the past year.

Police and soldiers struggled throughout the day to enforce order over a widespread area, firing shotguns, rubber bullets and tear gas at roving bands of residents who pelted them with rocks, bottles and homemade gasoline bombs. The rioting that began yesterday in two townships after police broke up a series of illegal but peaceful demonstrations spread like an uncontrollable brush fire today to neighboring communities.

Angry mobs set up hundreds of makeshift barricades of burning tires, mattresses and refuse to block police access to the rubble-strewn streets. Columns of black smoke mingled with clouds of tear gas throughout the area.

[In Washington, a senior U.S. official stepped up criticism of the South African government, saying that negotiations "leading to the end of apartheid" could not be achieved with continuing "jailings and beatings and bombings and burnings."]

By nightfall, security forces were still battling residents in at least six townships, all of which had been cordoned off to the press and public by ministerial order. Witnesses described a ring of fire they said was visible over a large area east of the city. The drivers of fire engines and ambulances refused to enter the area for fear of attack.

Like yesterday, most of the deaths occurred in the black townships of Guguletu and Nyanga where police again opened fire on stone-throwing crowds. Among the dead was a 3-year-old boy killed when members of a mob threw a gasoline bomb at his house, according to the state-run television network. Police reported 89 arrests.

At least three persons were killed in the mixed-race or Colored township of Mitchell's Plain, a relatively affluent collection of well-kept houses and shops that up until today had been untouched by the violence. By tonight it, too, was ablaze, with angry youths stoning police vehicles.

At least five public schools here and in nearby Manenberg township were also turned into battlegrounds today. Police stormed school grounds to disperse protesting students, according to the South African Press Association, which said local reporters saw police pumping shotgun rounds toward one Mitchell's Plain elementary school and lobbing tear gas into the grounds of at least four high schools. Classrooms at one Manenberg school were gutted by fire.

At a Methodist day care center here, witnesses said workers frantically rounded up small children and bundled them into the building as clouds of tear gas wafted over the yard.

Today's violence followed yesterday's attempted protest march when police put on a massive show of physical force in crushing attempts by thousands of demonstrators to march to Pollsmoor Prison outside Cape Town. The protesters had planned to demand the release of jailed black nationalist leader Nelson Mandela, serving a life term at the prison.

The police crackdown turned many of the demonstrators into angry rioters in Guguletu and the nearby Colored township of Athlone. They began a night-long spree of arson and stonings that continued throughout today and spread throughout the area east of Cape Town.

None of these townships is in the area under the government's five-week-old emergency rule. But their eruption in recent days is further evidence that officials have yet to find an effective strategy to quell political violence.

Trouble came to Mitchell's Plain this morning when students at a local high school boycotted classes. Police arrived on the scene and used plastic whips to break up a crowd of students in the school yard, according to witnesses.

The confrontation set off a chain reaction of violence. Students set out for a nearby shopping center where they smashed windows and burned and looted stores. Police responded with shotgun fire and tear gas. Students at other schools then started demonstrations and police began invading school grounds throughout the township.

A police van smashed through a locked gate at the Mondale high school and police peppered the yard with tear gas. At Spine Road secondary school they jumped fences, threw tear gas into three clasrooms and lashed fleeing teachers and students with plastic whips, witnesses said.

Family members said a 16-year-old grocery store clerk was killed. The Cape Times newspaper reported two more deaths tonight.

At Guguletu, police said one man was shot dead when he and a companion attacked a four-man police patrol with knives late last night. Another 16-year-old reportedly died after he bled to death from bullet wounds in his arm, a police spokesman said.

Police also used tear gas and whips to disperse about 75 picketing students on the campus of the University of Cape Town, a predominantly white school. There were also new confrontations between police and students at the University of the Western Cape, where the Rev. Allan Boesak is a chaplain. Boesak, an organizer of yesterday's march, was arrested earlier this week under South Africa's sweeping internal security law.

The other deaths reported by police today included a black man shot by police in Soweto and a Colored man killed in the western Cape Province town of Paarl. The third death was of a 19-year-old black man killed by a police rubber bullet in Kwa Thema, a township east of Johannesburg.

Also today, a regional prosecutor said charges would be dropped against nine journalists arrested yesterday at Athlone township for allegedly disregarding a police order to leave the scene of a confrontation with students.