Seoul police are looking into suspicions that the main opposition party engaged in massive online opinion rigging during elections, including the 2007 presidential vote.

A newspaper reported Wednesday that the Liberty Korea Party used a computer program to spread favorable news and jack up "likes" on comments on Internet sites from 2006 to 2014. At those times, the party's name was first the Grand National Party and then the Saenuri Party.

The report cited the party campaign office's chat records that it secured from an insider.

"We are checking the authenticity of the report," the Seoul Metropolitan Police Agency said.

The agency has probed a similar online manipulation scheme led by an arrested blogger linked to the ruling Democratic Party.

The blogger known as Druking used the same software. In a recent letter sent to a news outlet, he said that he acquired the program from a campaign official of the Grand National Party. It was used during the 2007 presidential election, he added.

The ruling party said it will file a complaint with the prosecution soon to investigate the opposition party's "crime against the constitutional order."

The DP's chief, Choo Mi-ae, issued an urgent instruction Wednesday to request a prosecution probe, party spokesperson Park Beom-kye said.

It will also demand the upcoming independent counsel probe into the Druking case be expanded to include LKP staff involved in the alleged opinion manipulation, he said in a message to reporters.

The revelation came one week before local elections and parliamentary by-elections slated for June 13.

The DP has been plagued by the Druking scandal. The prime suspect is suspected to have frequently contacted Kim Kyoung-soo, a former close aide to President Moon Jae-in and the party's candidate for South Gyeongsang governor.(Yonhap)