Foreigners held in a Japanese immigration detention centre have launched a hunger strike over the death of a detainee, drawing fresh attention to conditions under which they are held.

An Indian man died in an apparent suicide on Friday at the East Japan Immigration Center in Ushiku, Ibaraki Prefecture. Activists have said the man killed himself a day after being denied release.

Detainees began refusing food on Sunday, with the strike since spreading to an unspecified number of inmates, Daisuke Akinaga, a spokesman for the center, said. He cited the Indian's death, long-term detention and inmates' inability to win temporary release as reasons for the protest.

The death was the 14th at a Japanese immigration detention center since 2006, a toll that has led to wide criticism over standards of medical care, the monitoring of detainees held in solitary and guards' responses to medical emergencies.

Immigration remains a prickly subject in Japan, where cultural and ethnic homogeneity remain deeply rooted even as the population shrinks and companies grapple with the worst labour shortages for more than four decades.