SEOUL, FEB. 26 -- South Korea's newly inaugurated president, Roh Tae Woo, announced a political amnesty today that left several noted dissidents in jail and disappointed many human rights activists.

The amnesty, Roh's first official act, came as police discovered a failed time bomb inside a U.S. cultural center in Kwangju. The device had been intended to go off at the same time as students occupied the U.S. cultural center here Wednesday, police said.

Roh decided to release about 125 political prisoners, leaving 260 in jail, according to official figures. Other sources said the number of prisoners still confined for antigovernment activities is considerably higher.

The partial amnesty was Roh's second act in recent days that disappointed Koreans who hope that their new president will make a clean break with the past. Before taking office, he appointed a Cabinet that retained most key ministers from former president Chun Doo Hwan's government.

"I expected more student leaders would be released," said Han Mi Soon, 29, a housewife. "I think the amnesty is big in numbers but not generous enough."

Among those not released was Kim Keun Tae, one of South Korea's best-known political prisoners and winner of the Robert F. Kennedy human rights award last fall. Kim initially was slated for release, according to knowledgeable sources, but hard-liners in Roh's new government won the battle to classify Kim as a "hard-core leftist" who should not be freed.

"It's too bad, because now this government is going to continue to have human rights problems," said one western diplomat. "Everybody's going to focus on who wasn't released, not who was."

Roh, a retired general and ruling party leader, was elected Dec. 16 and inaugurated yesterday in this country's first peaceful transition of power. He promised a new era of democracy and reconciliation, but many Koreans remain skeptical because of Roh's close ties to Chun, who came to power in a coup.

"This shows there's no difference from the former regime," said Rhee Kyoung Bae, an official with the National Council of Churches, referring to the amnesty. "They must clean up all the past cases if they want people to have a new impression."

The release of 125 political prisoners was part of a general amnesty affecting more than 7,000 criminals, parolees and others. Such amnesties have been a Korean tradition since the Yi Dynasty began in the late 14th century, when new kings would set prisoners free.

A government spokesman, Chung Han Mo, said tonight in a statement that "this act of leniency" is intended to promote "grand national reconciliation and democratic development." Political prisoners were released "if they have renounced their previous radical beliefs," he said.

Chung added that "it is very regrettable, however, that those who fundamentally reject free democracy," among others, could not be released.

The government said that 1,700 political offenders would be affected by the amnesty. Most of those cases, however, involved people who are not in jail but will have their civil rights restored, their suspended sentences dropped or -- in the case of 68 teachers fired for political reasons -- their jobs returned.

Officials said that 125 political prisoners will be released from jail Saturday. Two hundred others awaiting trial and 60 convicted of political offenses will not be released, they said. Less than two months ago prosecutors said there were 1,160 people convicted or awaiting trial for antigovernment offenses, according to the Korea Times. Some human rights activists said they believe there are several hundred political prisoners still in jail.

Chun's regime was frequently criticized for human rights abuses. Two widely publicized police torture cases last year, one resulting in a student's death, helped generate the political pressure that eventually forced Chun to permit the December election.

Several of those passed over today have been cited by human rights groups -- such as Amnesty International or Asia Watch -- as having been indicted for political offenses, tortured or unfairly tried.

Kim Keun Tae, a former student leader and labor organizer, was arrested in 1985 and charged with violating the National Security Law, which makes it a crime to say anything that resembles North Korean propaganda. Kim also was accused of organizing meetings "feared to cause common unrest."

He was held incommunicado for two weeks after his arrest and, he has testified, beaten and tortured with electric shocks.

Prisoners kept in jail included Chang Ki Pyo, who was arrested for allegedly inciting a violent rally in Inchon two years ago. He also was held incommunicado, without access to lawyer or family, and severely beaten, according to Asia Watch.

Lee Tae Bok, also not released, was arrested in 1981 and charged with publishing books "calling for class struggle." He also was accused of leading "antistate" organizations. At his trial, Lee said he was tortured until he confessed to being a communist. His sentence to life in prison was reduced to 20 years in 1983 and, today, to 15 years.

South Korean officials say they must restrict some freedoms because of the threat from communist North Korea. North Korean agents repeatedly have tried to infiltrate the South to commit terrorist acts or organize radical groups, according to South Korean intelligence agencies.

Government opponents here respond that South Korea uses the North Korean threat as an excuse to jail opponents of authoritarian rule here.Special correspondent Peter Maass contributed to this report.