South Korean dissident leader Kim Dae Jung stepped off a jetliner here this morning, ending a two-year exile, and was promptly roughed up by government security men.

The fight occurred as thousands of people, many of them waving posters bearing Kim's portrait, lined the streets leading from the airport, hoping for a glimpse of him.

According to two U.S. congressmen who were with him, Rep. Edward F. Feighan (D-Ohio) and Thomas M. Foglietta (D-Pa.), Kim was punched repeatedly in the face and body by security men when he resisted being put into an elevator at Seoul's Kimpo Airport.

The two congressmen said they and former U.S. ambassador to El Salvador Robert White, were thrown to the floor.

"It was a disgraceful exhibit of unnecessary force," Foglietta said.

Patricia Derian, former assistant secretary of state for human rights, who was also present, called the security men a "group of thugs."

After the fracas, Kim was taken by a government van to his house in Seoul's Dongkyo-dong district.

There security men blocked access to reporters, saying Kim was tired. According to a government statement, Kim will be allowed to come and go freely in the conduct of his "private affairs."

This apparently means that police will block his exit from the house if they believe that he is going to engage in politics. He has been banned by President Chun Doo Hwan from taking part in politics.

Young demonstrators, some of them apparently factory workers, and others wearing suits and ties, surrounded a press bus entering the city today and repeatedly chanted, "Kim Dae Jung, Kim Dae Jung".

Kim arrived home with an entourage of 30 Americans, who said they were trying to ensure his security, and about 130 foreign journalists.

Before landing in Seoul, they decided that they would not allow themselves to be separated from Kim at the airport.

Ambassador White said he planned to meet with the U.S. ambassador, Dixie Walker, and demand that a formal protest be made of their treatment.

Last night, during a stop in Japan, Kim reopened a dispute with Japanese authorities over his kidnaping in Tokyo by South Korean agents 12 years ago.

Japanese police investigators were waiting at Narita Airport to question him about the abduction when he landed, but Kim told a press conference that he refused the request. Time was short, he said, and "I am very much skeptical with the Japanese government's attitude, whether it really wants to find the truth."

Five days after his disappearance from a Tokyo hotel in August 1973, Kim turned up blindfolded and beaten outside his home in Seoul. He was then put under house arrest.

A delicate political compromise over the incident settled a diplomatic row between the two countries.

Kim, who was narrowly defeated in a presidential election in 1971, has been living in exile in the United States for the past two years.