A key witness in a case of alleged evidence forgery framing a North Korean defector for espionage was in a life-threatening condition Thursday after attempting suicide, prosecution officials said.

The witness, an ethnic Korean with Chinese nationality whose name was withheld, is suspected of obtaining the fake evidence, including documents purporting to be the defector's immigration records, and handing it over to the National Intelligence Service.

The case of Yoo Woo-seong, a 34-year-old former civil servant for the Seoul municipal government, has raised a political storm in South Korea amid mounting suspicions that the NIS helped the prosecution in the trumped up spy scandal.

The Korean-Chinese was found by police officers around Wednesday noon at a motel in Seoul's southwestern Yeongdeungpo district, officials said, adding that he was immediately sent to a nearby hospital where he remains in critical condition.

The prosecution officials suspect that the witness, who had undergone questioning by prosecutors until dawn on Wednesday, attempted to take his own life on the same day.

Yoo, previously a Chinese national in North Korea, was indicted last year on charges of handing over the personal information of more than 200 North Korean defectors to Pyongyang after disguising himself as a defector in order to enter South Korea.

 After a local court acquitted Yoo of espionage, prosecutors appealed the verdict and submitted Chinese immigration records apparently showing that Yoo entered North Korea on May 27, 2006 and left through China on June 10, 2006.

At the request of a Seoul appeals court, however, the Chinese Embassy in Seoul examined the records and announced them to be fake.

Amid the mounting suspicions, the Seoul Central District Prosecutors Office launched a preliminary investigation team to look into whether the immigration records were fabricated. (Yonhap)