CONCORD, CALIF., SEPT. 5 -- The wife of Nicaraguan President Daniel Ortega joined thousands of protesters today honoring a peace activist maimed as he tried to block a munitions train. Some demonstrators ripped up tracks stained with his blood.

Jesse L. Jackson spoke and Joan Baez sang at the protest against U.S. policy in Central America, which was staged outside the Concord Naval Weapons Station.

The rally saluted peace activist S. Brian Willson, who was run over last Tuesday by a two-car Navy train carrying explosives to Port Chicago, presumably for shipment to U.S.-backed Nicaraguan rebels. One of his legs was severed and the other had to be amputated.

Demonstrators tore up eight sections of rail and the ties beneath them and erected a six-foot-high barricade at a closed station entry.

Deputy sheriffs backed by Marine guards, both stationed behind concertina wire strung along the base boundary, made no effort to halt the dismantling of track or erection of the barricade.

No arrests were reported by the Contra Costa County Sheriff's Office but protest leaders said several people were held for throwing rocks. Protest leaders said 7,000 people took part in the demonstration while the sheriff's office estimated the number at 3,800.

Comparing Willson to famous martyrs, Jackson said, "Our hero is not Ollie North going south, it's Brian Willson."

Rosario Murillo, Ortega's wife, visited Willson in John Muir Hospital in Walnut Creek before the rally at Clyde Park and said she was "amazed" by his strength and passion for peace. She called her visit "painful" but said it filled her with hope.

"He dreams of having a small house in the mountains of Nicaragua where he can work with the peasants," she said.

Jackson led a procession to the tracks, knelt on them and prayed. "There's no greater sacrifice than to give up your legs that a nation might walk," he said.

Afterward, the demonstrators built a shanty on the tracks.

Willson's wife, Hollie Rauen, spoke to the crowd and played a tape recording from her husband in the hospital.

"Only we can bring peace," Willson said on the tape. "I really believe we have peace in our hands if we want to pay the price of peace -- nonviolent revolution."

A Navy team from Washington is investigating the train incident.