By Thomas Wilson

TOKYO (Reuters) - Fourteen inmates in a Japanese immigration detention center are on hunger strike over what they call "inhumane conditions" including poor medical care, drawing fresh attention to the country's detention system.

The detainees launched their hunger strike at the center in the city of Osaka on Monday over the rejection of their applications for provisional release, the Osaka Regional Immigration Bureau said.

The hunger strikers are also protesting against inadequate medical care and long-term detention, a detainee at the center and Nobukazu Nagai, of the Provisional Release Association in Japan, told Reuters.

One inmate has not eaten for more than two weeks, they said.

A spokeswoman for the bureau, Mahomi Oiwa, said the facility was not aware of any complaints about medical care or length of detentions.

No health problems had occurred among the hunger strikers, and officials were continuously asking them to take food, she said.

A Reuters investigation this year into the death at a Tokyo facility of a Sri Lankan, revealed serious deficiencies in medical treatment and monitoring in the immigration detention system.

Guards with little training made critical decisions about detainees' health, and doctors visited some main detention centers as infrequently as once a week, the investigation found.

Since 2006, a dozen people have died while in detention, including four cases of suicide.

"We are being held in inhumane conditions," the hunger strikers said in a statement to the bureau seen by Reuters.

"Because of prolonged confinement with very inadequate medical care, we are suffering from illnesses both physical and mental."

Inmates at the Osaka facility are forced to wait days for medical checks, and are in all but the most serious cases refused access to doctors, said Nagai and the detainee, who spoke by telephone from the facility but was not among the hunger strikers.

In February, more than 40 detainees launched a hunger strike at the Osaka center to protest against what they said was poor medical care.

(Reporting by Thomas Wilson; Editing by Robert Birsel)