SEOUL, JUNE 10 -- Seoul erupted into its worst political violence in years this afternoon, as thousands of angry antigovernment protesters fought riot police in four hours of rugged street battles that at times saw the usually unshakable police retreating in panic.

Rioters burned at least one police kiosk and reportedly attacked an office of the ruling Democratic Justice Party. They built barricades, lit bonfires and threw so many stones that streets all over Seoul's central sector were littered with rubble.

Police, who had banned the rally, blanketed a huge swath of Seoul with tear gas. It invaded shops, offices and homes and left many people who had nothing to do with the protests gasping for breath. Calm was restored tonight.

The demonstration came on what was supposed to be a day of glory for the government. Several hours earlier, ruling party chief Roh Tae Woo had been formally nominated at a convention as successor to President Chun Doo Hwan.

{In Washington, State Department spokeswoman Phyllis Oakley deplored the violence, saying, "In our view, political progress in Korea would be furthered by greater willingness to engage in dialogue, rather than coercion, of compromise rather than violence." She added that the United States urges "all Koreans to work sincerely and selflessly toward a broadly based political system."}

The day's events contrasted sharply with opposition demonstrations in Seoul in recent months, which the government rapidly suppressed with massive police force. At one point today, protesters overran a contingent of police who had run low on tear gas, their main weapon. Officers were stripped of their equipment and battered with rocks, with at least one suffering a serious head injury.

Protests also occurred in Pusan, Kwangju, Masan and other provincial cities -- a total of 11, according to the semiofficial Yonhap News Agency.

National police director Kwon Bok Kyung said that 2,392 persons had been arrested in Seoul and 1,439 in other cities. He added that 16 government buildings and 23 police and other vehicles were burned or destroyed. Kwon also said that 708 police and 24 civilians were injured.

The rallies were called to protest the ruling party convention and the death of a student during police torture in January. The opposition sees the convention as part of a process to perpetuate what it called a "military dictatorship" in South Korea.

Emotions appeared to have risen with reports that another student had died after a tear gas grenade hit him on the head yesterday. Officials tonight said he was still alive but only because he was on life-support equipment..

Rows of police in visored helmets and military fatigues fired volley after volley of tear-gas grenades from special rifles. People riding buses and cars through the area choked along with protesters on clouds of tear gas.

Protesters at one point took over the lobby of the luxury Lotte Hotel, sitting on its marble floor and singing political songs. Riot police stormed in to drag them away but were forced into a corner when they were outnumbered.

Throughout the day, people chanted, "Down with dictatorship." Others charged the United States with supporting the Chun government. By plan, at 6 p.m. cars began honking their horns and church and temple bells were rung as a sign of opposition to the government.

Kim Young Sam, president of the main opposition Reunification Democratic Party, rode a car moving slowly through the streets, drawing cheers from demonstrators.

At one point, about a dozen student radicals appeared at a street corner, each holding a lighted gasoline bomb. Several minutes passed before police noticed them and sent dozens of tear-gas grenades arcing toward them.

The students then tried to hurl their bombs over six lanes of busy traffic to hit the police. Most of the bombs fell short and exploded on the street, with terrified drivers plowing through flames. No one appeared to be hurt, however.

Elsewhere in the city, about 500 people were said to have commandeered a subway train.

Several hours earlier, Roh had delivered an acceptance speech before about 8,000 delegates at the ruling party convention in an air-conditioned gymnastics stadium in Seoul. He sounded a theme of continuity with the policies of Chun's seven-year-old government.

He said he was willing to reopen dialogue with the opposition on constitutional reform, which Chun suspended in April. But any change, he said, would come only after Chun steps down next spring and the Seoul Olympics are held in September.

Roh added that by that time the opposition would be ready to accept the parliamentary system that the ruling party wants. The main opposition party demands an immediate constitutional revision and one that would put into effect its favored system of government, one headed by a directly elected president.