OSAKA — Nearly two dozen Vietnamese being held at the West Japan Immigration Center in Ibaraki, Osaka Prefecture, are on a hunger strike to protest their prolonged incarceration.

The hunger strike began Tuesday night, after the group sent an appeal to lawyers and human rights groups, saying that they had been held at the center for an unreasonable length of time.

Some have been held at the center for nearly two years.

“We are really disappointed and our spirits, like our bodies, are collapsing due to our unreasonable detention,” the group wrote in its appeal.

“The hunger strike began with 25 people, but at the moment there are 23 hunger strikers, including two women. Their ages range from early 20s to early 50s, and some have been held since 2002,” said Michitsune Kusaka, a member of the Rights of Immigrant Workers in Kansai (RINK) on Thursday.

Junichi Hiroishi, spokesman for the West Japan Immigration Center, would not comment on the hunger strike, saying only that it was the policy of the center to ensure that all detainees ate properly and had access to medical care.

The 23 were boat people who arrived in Japan between in 1989 and 1991 before being granted residency status.

All have served time in Japanese prisons for murder, theft and other serious crimes.

After being released from prison, they were ordered deported and placed in the detention center.

However, because of their status as former boat people, the Vietnamese government has refused to take them back.

In November, some of the current hunger strikers filed a lawsuit with the Osaka District Court, charging that they they were being unfairly detained after having served their prison time. They demanded to be released.

In a letter issued a few days before they began their hunger strike, the Vietnamese protested that conditions at the center, including solitary confinement and rough treatment by the guards, are so severe that one detainee had killed himself.

In October 2001, a Vietnamese man, whose identity has not been released, reportedly committed suicide inside the center. The suicide led to the formation in the spring of 2002 of a network of Kansai human-rights NGOs, including RINK, that keeps an eye on the conditions of the detainees.

Kusaka and other activists say the odds of their being granted a release anytime soon are very slim.

On Friday, the group’s lawyers were expected to meet with some of the hunger strikers who have filed the lawsuit to prepare for their next session at the Osaka District Court on June 23.

A senior official of the Justice Ministry’s Immigration Bureau said the government has been asking Hanoi and the Vietnamese Embassy in Japan to promptly accept their return.

But he said that it is still unclear if Vietnam would accept them. The country does not usually accept people who have been recognized as refugees overseas and are unwilling to return to Vietnam, the official said.

He said the ministry acknowledges the human-rights problem of detention for an indefinite period and claimed that it usually releases such foreigners on bail until deportation procedures get under way.

“But given the criminal records (of the Vietnamese), it is difficult (for a law-enforcement authority) to show too much leniency,” he said.