The main opposition Democratic Party staged a rally Wednesday, upping its offensive against the government and prosecution over allegations that state investigators fabricated Chinese documents in a high-profile espionage case.

Dozens of DP lawmakers renewed their calls for a parliamentary inquiry and an independent-counsel probe into the case during their first rally in three months at Gwanghwamun Square in central Seoul.

The ruling Saenuri Party decried the street gathering as politically-motivated just three months ahead of the major local elections, calling on DP lawmakers to return to the parliament to focus on their legislative obligations.

“The alleged fabrication of court evidence is a symbolic case that has brought to the fore the real face of the Park Geun-hye government,” said DP leader Kim Han-gil during the rally.

“We believe that our citizens, by now, have gotten a full grasp of why we have persistently called for a major reform of the prosecution and the National Intelligence Service.”

The prosecution is accused of falsifying documents it submitted to a Seoul appellate court as evidence to back its claim that Yoo Woo-seong, the defendant, returned to North Korea and then entered China in 2006 for espionage activities.

Prosecutors argued that they obtained the documents from provincial security authorities in China through legitimate diplomatic channels. But the Chinese Embassy in Seoul said last week that the documents were forged.

Yoo, who defected to the South in 2004, was indicted last February on charges that he handed over to Pyongyang the personal data of some 200 North Korean defectors while working for the Seoul municipality. A lower court cleared him of the charges last August, citing inadequate evidence to convict him.

The authenticity of the three documents has been called into question.

One of them entails records of Yoo’s travel between the North and China, and the prosecution argues security authorities in the northeastern Chinese city of Helong issued it.

Another document, also issued by Helong authorities, reaffirms the authenticity of the travel records, while the other carries the Chinese authorities’ confirmation that the travel records submitted by the defendant to the court were not legitimately written.

During a parliamentary session, Justice Minister Hwang Kyo-ahn reiterated that investigators did not fabricate any documents. But he stressed that a thorough investigation is needed to “uncover the truth.”

A day earlier, Foreign Minister Yun Byung-se told the parliament that two of the three documents were not obtained through the South Korean consulate in China’s northeastern city of Shenyang. His remarks further reinforced the allegations of the falsity of the documents.

On Wednesday, Cho Baek-sang, consul general at the consulate, backed Yun’s remarks, reiterating that he obtained only one of the three documents from the Chinese authorities.

The Seoul government has been increasingly cautious in the handling of the burgeoning fabrication scandal as it could escalate into a diplomatic issue with Chinese authorities challenging the authenticity of Korean prosecutors’ court evidence.

In defense of the government, the ruling party criticized the DP for “siding with an alleged spy” and called on it to wait until an internal investigation verifies the truth behind the scandal.

“DP lawmakers took to the street again, taking the side of a man put on trial for espionage charges,” said Saenuri floor leader Choi Kyung-hwan during a meeting of senior party members.

“The truth has yet to be verified. But the case could escalate into a diplomatic issue, should it continue to be politicized.”

By Song Sang-ho (sshluck@heraldcorp.com)