Protesters carry coffins to symbolize what they say were deaths at the hands of former graduates

FORT BENNING, Georgia (CNN) -- Thousands of demonstrators gathered Sunday in the largest-ever protest against the U.S. Army's School of the Americas, a military training center which opponents say turns out a steady stream of Latin American dictators, torturers and rogues.

The demonstration has been staged annually since 1990 to protest what participants call the "School of Assassins." They say Latin American graduates use what they have learned at the school to violate human rights in their homelands.

Army officers say the school has helped advance democracy in Latin America and that it has reformed its curriculum to stress respect for human rights.

Sheen says the School of the Americas is an embarrassment to the Army

Actor Martin Sheen was among those who addressed the protesters, many of whom carried white crosses they said represented victims of some of the school's almost 60,000 graduates.

"We honor our Army, we respect their mission, but this is not part of that mission. This is an embarrassment to the Army," Sheen said.

Some protesters marched onto the grounds of the U.S. Army's Fort Benning, which has housed the school since it moved from Panama in 1984.

According to Columbus police officer Frances McDaniel, the protesters offered little resistance when they were placed on buses, driven out and dropped off on city property

No one was arrested, McDaniel said. But past protests have resulted in arrests and jail terms. Federal courts have ruled that military installations can restrict political and partisan demonstrations.

Organizers estimated the crowds at 7,000; Columbus police spokesman Lt. M.C. Todd put the figure at fewer than 2,500.

U.S. Rep. Joseph P. Kennedy II of Massachusetts is among those who have complained about the School of Americas, located about 85 miles southwest of Atlanta. Opponents in Congress have tried without success to cut funding for the school.

Graduates of the school include former Panamanian strongman Manuel Noriega, former Argentine dictator Leopoldo Galtieri, Haitian coup leader Raoul Cedras and the late Salvadoran death squad organizer Roberto D'Aubuisson.

Thousands gather in what has become an annual protest

The gathering was larger than eight previous annual protests, which mark the anniversary of the November 16, 1989, killings of six Jesuit priests by a Salvadoran army unit. The school trained 19 of the 26 soldiers implicated in the deaths by a U.N. investigation.

"We gather here to honor our brothers and sisters in Latin America," the Rev. Roy Bourgeois, a protest leader, told supporters. "We will close the School of the Americas."

More than 600 of the roughly 2,000 demonstrators last year were arrested when they entered the military post.

About three dozen people who had been arrested for previous protests were convicted of criminal trespass earlier this year and sentenced to six months in prison and fined $3,000 each.

Fort Benning officials held a debate about the school Saturday, but opponents declined to participate when they were told they could not carry cardboard coffins onto the buses that would transport them to the event.

Reuters contributed to this report.