HARBEL, LIBERIA, MAY 27 -- Rebel troops today fought artillery and mortar battles with government soldiers at a checkpoint that controls a main road to the capital only 35 miles away, witnesses said.

Residents said they heard artillery shells, mortars and machine-gun fire as rebels attacked the army checkpoint at the northern end of the world's largest rubber plantation, southeast of the town of Kakata.

The outcome of the fighting was unclear. Rebels of the National Patriotic Front have been fighting for five months to topple President Samuel Doe, whom they accuse of corruption and violations of human rights.

Capture of the checkpoint would leave the rebels in control of a main road that controls access to many parts of the country, including the capital of Monrovia to the southwest. It is also the only road leading to the Bong iron ore mine, one of the last major economic enterprises remaining in government hands.

On Saturday, rebels captured a checkpoint north of Kakata. Hundreds of civilians fled the weekend fighting and took refuge in and around the nearby town of Harbel. The town is located on the rubber plantation, which is owned by Bridgestone-Firestone Inc., a U.S. subsidiary of the Japanese Bridgestone company.

Plantation sources said 10,000 people have taken refuge here during the last two weeks. The rubber plantation, the world's largest, is Liberia's largest employer, and 75,000 people live here.

Diplomats and other sources said today that the rebels still controlled Buchanan, the country's main port. The government last week claimed that it recaptured the city, about 90 miles south of Monrovia.

Rebel spokesman Tom Woewiyu, speaking by telephone late Saturday from his home in East Orange, N.J., said he has been holding talks with State Department officials in Washington who are trying to get rebel and government officials to negotiate an end to the fighting.

But, he said, the rebels will not open talks unless Doe resigns and surrenders to stand trial for "murder, genocide, human rights abuses" and other alleged crimes.

International organizations and the U.S. Congress earlier condemned government forces, saying they had killed hundreds of civilians in their efforts to defeat the rebels.