SEOUL, South Korea (AP) _ Peaceful Buddhist monks, angry workers and violent radical students protested separately today, demanding the ouster of President Roh Tae-woo for allegedly suppressing their rights.

Police fired tear gas to stop 5,000 workers in the port of Masan from marching from an export industrial complex to the streets, news reports said.

Protesters accused the government of trying to suppress the labor movement. They demanded investigations into attacks on union offices in the industrial complex, according to Seoul's Chosun-Ilbo newspaper. Masan is 200 miles south of the capital.

In central Seoul, 1,500 gray-robed Buddhist monks gathered with their supporters at Chogyesa Temple shouting, ''Down with the government which suppresses Buddhism 3/8'

The monks issued a statement vowing ''to terminate the authoritarian rule of Roh's government.''

They were protesting the arrest of Lee Ji-kwan, president of Seoul's Buddhist-run Dongguk University, for allegedly selling college places. Lee was freed, but Buddhists claim the government trumped up the charge.

Students rallied in three cities today to demand the release of a radical student jailed for traveling illegally to North Korea.

''Overthrow the Roh regime which suppresses the masses 3/8'' an organizer told the Seoul rally, which included students from more than 30 schools.

''Realize unification through struggles against the United States,'' said a student statement supporting unification with communist North Korea. Radicals, a small but vocal minority, feel the presence of 43,000 U.S. troops stationed in South Korea hinders unification.

In Pusan, 1,600 students from three colleges battled riot police with firebombs and rocks to demand the ouster of the government and the release of Im Su-kyong, a 20-year-old student who traveled illegally to North Korea to attend a youth festival in July, the official Yonhap news agency reported. Peaceful rallies were held at three other Pusan schools, it said.

In Suwon, just south of Seoul, 700 students from eight schools clashed with riot police in an anti-government protest on a street in front of Sunkyunkwan University, and eight students were arrested, Yonhap said.

The most violent scenes took place in the capital, where more than 1,000 combat-clad riot police and four armored vehicles firing tear gas stormed onto Seoul National University campus to break up a rally of 3,000 students.

''Overthrow Roh Tae-woo 3/8'' students screamed before they fled, coughing and choking in tear gas so thick campus buildings could not be seen. They regrouped, pelting police with hundreds of large rocks and lunging at them with metal pipes. But the black-helmeted police held the campus gates.

Witnesses said two dozen cars in a campus parking lot were smashed by rocks thrown by both sides. There were numerous injuries, but no arrests were made.