Fidel Castro accused the United States of wanting to attack Cuba, speaking at a May Day celebration on Thursday that aimed to defend the island's socialist system against criticism from abroad.

"In Miami and Washington they are now discussing where, how and when Cuba will be attacked," the Cuban president told a crowd of hundreds of thousands gathered for the celebration in Havana's Plaza of the Revolution.

"I want to convey a message to the world and the American people: We do not want the blood of Cubans and Americans to be shed in a war," he said.

The crowd responded with cries of "Whatever it takes, Fidel!" while waving handheld Cuban flags. One group hoisted an effigy of President Bush that read, "Bush: Don't mess with Cuba."

Castro spoke for less than two hours -- brief for the 76-year-old president. He said U.S. officials "provoke and encourage" attacks like the recent hijackings of Cuban planes and boats.

There was no immediate response from the U.S. State Department. Defense Secretary Donald H. Rumsfeld said recently that "there are no plans for military action against Cuba."

May Day events were also held elsewhere in the world and some turned violent:

--In Germany, youths set cars alight and pelted police with stones, bottles and fireworks Thursday in a Berlin neighborhood famed for its May Day clashes after some 5,000 protesters staged a peaceful march in support of a variety of leftist causes. Police used tear gas and water cannons to disperse troublemakers.

--In Venezuela, gunshots rang out at a rally against the government of President Hugo Chavez in Caracas, leaving one dead and one wounded, officials said. Police fired tear gas and rubber bullets to disperse demonstrators angered by the shooting. The Opposition is seeking a referendum on Chavez's rule, accusing the leader of attempting to amass too much power.

--In Moscow, diverse Russian political forces marched in competing rallies. About 15,000 people gathered at the Communist Party's march, calling for the government's resignation. During the Cold War, tens of thousands of Russians flooded Red Square on May 1 in rallies meant to demonstrate loyalty to the communist state and solidarity with workers abroad.

--In Asia, thousands of people in Indonesia, South Korea and the Philippines celebrated May Day by protesting for higher wages, shorter work weeks and political change.

The gathering in Cuba came two weeks after the firing-squad executions of three men convicted of terrorism for trying to hijack a Cuban ferry full of passengers to the United States. No one was hurt in the hijacking -- one of at least four over a few weeks.

The Bush administration -- along with other governments and international human rights groups -- condemned the quick trial and execution of the men.

Castro said the executions were necessary to halt the hijackings and stem a growing migration crisis.

But he said he respected the opinions of Pope John Paul II and some of his longtime supporters, including the New York Rev. Lucius Walker Jr., who have asked him to abolish the death penalty. The Cuban leader said he would consider their arguments.

"Cuba, you are a world leader in human rights and respect for human life," Walker told the crowd earlier in the morning. "The death penalty demeans that."

Walker, pastor of Salvation Baptist Church in Brooklyn, and executive director of New York-based Pastors for Peace is among Cuba's best-known American supporters.

"The day will come when we can accede to the wishes for the abolition of this penalty so nobly expressed here by Reverend Lucius Walker," Castro said. "A wave of hijackings had been unleashed and was already in full development -- it had to be stopped."

Cuba also faces stern criticism for sending 75 dissidents to prison on charges of collaborating with U.S. diplomats to destabilize the socialist regime. It was the island's harshest crackdown on opponents in decades, drawing condemnation even from leftist intellectuals traditionally sympathetic to Cuba.

Castro said he was disheartened with "those friends of Cuba" -- such as Mexican novelist Carlos Fuentes -- who have "attacked Cuba unjustly."

He warned they would "suffer infinite sorrow" if Cuba were attacked and "they realized their declarations were shamelessly manipulated by the aggressors to justify a military attack."