The protest comes after UN rights envoy Jorge Bustamante in March raised concerns about Japan's often years-long detentions of illegal migrants, including parents with children as well as rejected asylum seekers.
"Those in the centre suffer such mental stress from being confined for so long," said Kimiko Tanaka, a member of a local rights group, about the East Japan Immigration Centre in Ushiku, northeast of Tokyo.
Japan keeps tight control on immigration and last year, despite generous overseas aid for refugees, granted political asylum to just 30 people.
Human rights activists, lawyers and foreign communities have complained for years about conditions at Ushiku and Japan's two other such facilities, in the western prefecture of Osaka and in southwestern Nagasaki prefecture.
At Ushiku, about 380 people are detained, with eight or nine inmates living in rooms that measure about 20 square metres (215 square feet), said Tanaka, a member of the Ushiku Detention Centre Problem Study Group."They are crammed into tiny segmented rooms that are not very clean, and many contract skin diseases," she told AFP.
The hunger strike protesters said in a statement that "foreigners are the same human beings as Japanese" and claimed that conditions are severe and their freedom to practise their religions is being curtailed.
"The Immigration Bureau has forced asylum seekers to leave voluntarily by confining them for a long time, making them give up on their religion, weakening their will and torturing their body and soul," they said.
"Japan, a democratic country, must not do such a thing, no matter what."
The protest erupted weeks after a Ghanaian man, Abubakar Awudu Suraj, died in unexplained circumstances in March as Japanese immigration officials escorted the restrained man onto an aircraft bound for Cairo.
"Police conducted an autopsy but could not find out the cause of his death," a Narita Airport police spokesman told AFP about the 45-year-old, whose Japanese widow has challenged authorities to explain.
Rights activists believe he was gagged with a towel, recalling a similar but non-fatal case in 2004 when a female Vietnamese deportee was handcuffed, had her mouth sealed with tape and was rolled up in blankets.
The protesters on hunger strike argue two recent suicides by hanging -- a 25-year-old Brazilian, and a 47-year-old South Korean -- also illustrate Japan's harsh treatment of inmates.
"Those were very unfortunate incidents," said an official at the Ushiku immigration centre who declined to be named.
"We recognise the largest problem is that an increasing number of foreigners here refuse to be deported, despite legal orders," he said.
The official also said the number of asylum seekers had doubled since 2008 mostly because of turmoil in Myanmar and Sri Lanka.
Last year 1,388 people, including 568 Myanmar and 234 Sri Lankan nationals, sought refuge in Japan.
Japan's immigration authorities have faced protests before. Two months ago, 73 foreigners at the Osaka centre staged a two-week hunger strike.
"We would have seen suicides like in Tokyo if they had waited longer," said Toru Sekimoto, who leads the local support group TRY, which successfully won the temporary release of most of the protesters.
Hiroka Shoji of Amnesty International Japan said: "The immigration facilities are supposed to be places where authorities keep foreigners for a short period before deportation.
"But some people have been confined for over two years as a result. The government must introduce a limit to detentions."
A Justice Ministry official who asked not to be named said: "The government will interview protesters at the centre and take appropriate measures."