Updated

Shots were fired at an opposition rally in a Caracas square Friday, killing at least three people and wounding 28, officials said. The violence erupted moments after opposition leaders announced they would extend and expand a general strike aimed at unseating President Hugo Chavez.

The shootings at Plaza Francia in eastern Caracas came as diplomats worked to restart negotiations to end the strike, which has paralyzed Venezuela's oil industry and brought political tensions to a boil.

Cesar Gaviria, secretary general of the Organization of American States, condemned the violence and said he would preside over an emergency meeting between government and opposition delegates late Friday.

Gaviria said he spoke with former President Carter, who has tried to mediate in Venezuela, and Carter backed his statement.

"The acts of violence today ... take place in a moment of maximum tension," Gaviria said. "It is urgent that the negotiations team meet as soon as possible and begin producing the results that Venezuelans expect from it."

Three people were killed and 28 people were wounded, said Leopoldo Lopez, mayor of Caracas' Chacao district where the plaza is located. Tearful citizens draped the body of one victim in a red, yellow and blue Venezuelan flag.

Two suspects were detained, said Angel Martinez, director of civil protection for Caracas' Chacao district. He had no more details.

Occasional bursts of gunfire spread panic in the plaza filled with hundreds of people listening to a speech. Several bloodied people were hustled into ambulances as dissident officers appealed for calm. Protesters bundled together on the ground to protect themselves.

Dozens of citizens scurried for safety inside the hotel, which serves as the dissidents' headquarters.

The plaza is the main rallying point for more than 100 military officers who declared themselves in rebellion on Oct. 22, demanding that Chavez resign.

A motive for the shooting was not immediately known. Vice President Jose Vicente Rangel and Interior Minister Diosdado Cabello condemned the incident. Cabello appealed for calm, saying federal police were investigating and urging the opposition not to rush to conclusions.

"We profoundly regret this incident," Cabello said. "We don't want this to be the beginning of escalating violence."

Almost immediately, however, some dissident officers and opposition leaders claimed that Chavez's government was responsible.

"Chavez is responsible for this crime!" dissident army Gen. Enrique Medina Gomez screamed into television cameras.

Thousands of Caracas residents banged pots and pans in protest. Less than an hour after the shootings, which occurred about 7 p.m. local time, several dozen people regrouped to wave Venezuelan flags and sing the national anthem.

Many had feared the outbreak of political violence as the strike extended into Venezuela's crucial oil sector and street rallies intensified. An attack on a central Venezuela newspaper early Friday by Chavez supporters increased those fears.

A shutdown of the oil industry raised the stakes in the strike, aimed at forcing a referendum on Chavez's presidency. Many Venezuelans accuse the populist Chavez of ruining the economy, courting communism and stirring class warfare in this deeply polarized South American nation.

The oil crisis forced the government to agree to restart talks — something it said it would not do until the opposition called off the strike.

Shipping agents said oil exports had stopped from Venezuela, the world's fifth-largest oil producer and a top supplier to the United States. Captains anchored tankers offshore, tugs stopped guiding ships through Venezuela's oil-rich Lake Maracaibo and dock crews stopped loading oil and natural gas.

Several refineries were shutting down in a process that takes several days. Since it no longer could fill orders, Venezuela's state oil monopoly freed buyers and sellers from fulfilling their contracts.

The government insisted that exports only were delayed. Energy Minister Rafael Ramirez said ships in port have a five-day "window" to depart with their loads.

The export shutdown meant workers were unable to pump as many as 500,000 barrels of crude from oil fields as scheduled, Ramirez said.

The United States depends on Venezuela for more than 10 percent of its imports of crude, the raw material for heating oil and gasoline. A prolonged shutdown — coupled with the threat of war in Iraq — could drive U.S. energy prices sharply higher.

"We can work around it for a couple of days. But if it goes on any longer than that, it could have a major impact on prices," said Phil Flynn, an analyst at Alaron Trading in Chicago.

Hundreds of Chavez supporters attacked the newspaper El Siglo in the central city of Maracay on Friday, and two employees were hospitalized with gunshot wounds, said newspaper vice president Tulio Capriles.

The U.S. Embassy denounced the "criminal aggression" and Gaviria called it "an assault on freedom of expression."

Venezuela's news media have become a major player in the conflict, with Chavez supporters complaining that most newspapers and television stations are mouthpieces for the opposition.

An oil industry shutdown and a general strike preceded an opposition march in which 19 people were killed on April 11.

Dissident officers ousted Chavez April 12. An interim government abolished the constitution, triggering a popular rebellion. Loyalist troops restored Chavez April 14.