SANTO DOMINGO, DOMINICAN REPUBLIC, DEC. 20 -- Nicaraguan rebels today launched their biggest offensive in the 7-year-old war against the leftist Nicaraguan government on the eve of peace talks in the Dominican capital, a rebel spokesman said.

Thousands of U.S.-backed contras began hitting targets before dawn in the gold-mining area of Nicaragua's eastern Zelaya province, said Bosco Matamoros, a spokesman for the rebel umbrella organization called Nicaraguan Resistance.

"Today at 4 a.m. we began the largest military operation of the war with approximately 7,000 of our men, which involves 11 regional commands and 45 task forces," Matamoros said in a telephone interview.

He said the objectives of the rebels are the towns of Siuna, Rosita and Bonanza, along with some landing strips in the area. He said their aim is to destroy the facilities that the government uses for gold processing.

In Managua, the Voice of Nicaragua, the official radio of the Sandinista government, confirmed rebels launched an attack in the mining region.

"Counterrevolutionary groups launched today at 5 a.m. local time a strong attack against the mining communities of Siuna, Rosita and Bonanza and waged heavy fighting," the announcer said.

A spokesman at the Defense Ministry in the Nicaraguan capital, who did not want to be named, also said the rebels had mounted an attack in the area but said he had no immediate details.

There was no immediate word from either side on whether the second meeting to try negotiate a truce will take place as scheduled on Monday.

Zelaya is a remote, jungle-covered province, and reporters are required to obtain a special permit from the military to visit war areas.

Asked why the operation came now, just before peace talks, Matamoros said, "This operation has been planned all along."