Three lawmakers of the Democratic Party went to the South Korean consulate in Shenyang, China on Tuesday as the party increased pressure over the alleged fabrication of evidence in an espionage case.

The case against former Seoul city official Yoo Woo-seong, who defected from North Korea in 2004, became a hot political issue after the Chinese Embassy in Seoul claimed new evidence submitted by the prosecution was falsified.

Yoo is accused of handing over information regarding around 200 Seoul officials to Pyongyang. He was initially acquitted of espionage charges in June last year, but the prosecution appealed the ruling with Chinese documents showing that Yoo traveled to North Korea as late as 2006.

Seoul officials say that the documents were issued by the security authorities in the northeastern Chinese city of Helong and were obtained through legitimate diplomatic channels.

The DP delegation, led by Rep. Shin Jae-kwon, was set to return later in the day after reviewing the documents submitted by the prosecution in an effort to determine how they were obtained.

Shim and Reps. Jung Cheong-rae and Hong Ihk-pyo will also interview a consul identified by the surname Lee. Lee is said to be the National Intelligence Service official who first obtained the documents.

As the DP seeks to prove their claims that the prosecution and the NIS used forged evidence, reports surfaced that China is investigating its officials linked to the case.

According to reports, China’s central government is conducting investigations into all immigration and security officials in Helong.

Citing unnamed sources, the reports also claim that China is penalizing concerned officials simultaneously.

The ruling Saenuri Party for its part is attempting to undermine the DP’s claims, raising suspicions that Yoo’s lawyers were collaborating with a pro-North Korean official with the Chinese Embassy in Seoul.

By Choi He-suk (cheesuk@heraldcorp.com)