Members of the Korean Confederation of Trade Unions' construction union hold signs in front of its office in Yeongdeungpo-gu, Seoul, where a search is underway Thursday morning. The signs read "Stop oppression of unions" and "We condemn the Yoon Suk Yeol regime."

Authorities have ramped up pressure on labor unions for two straight days, with police seizing documents at the offices of the two umbrella labor unions of the country over illegal activities at construction sites, Thursday,

Seoul police sent investigators to five construction workers' offices under the Korean Confederation of Trade Unions, three offices of the Federation of Korean Trade Unions and eight houses of related officials from 8:10 a.m. Thursday, securing information on union operations and accounting.

Police have reportedly retained evidence of illegal activities such as forcing companies to hire union members and demanding money or valuables from companies that had refused.

The KCTU construction union has contended it is "unfair" to raid the union, as the member identified as a suspect of illegal activities has already been expelled due to corruption.

Jang Ok-ki, head of the construction union under the KCTU, held a press conference in front of the union office in Yeongdeungpo-gu, Seoul, and lambasted that the government was committing unfair suppression of labor workers.

"Construction workers are being killed every year, but the lives of workers are not valued and the regime is taking the side of companies, suppressing our legitimate union activities," said Jang.

Police have been pushing for a special crackdown on "organized illegal activities such as extortion and violence at construction sites" for 200 days beginning December 2022. Since then, Police have opened investigations into 13 cases, booked 126 labor union officials and arrested two.

"We will no longer stand by and watch illegal activities at construction sites," Yoon Hee-keun, head of the National Police Agency, said in a national police conference in December. "We declare that we will root out collective illegal activities at construction sites and establish the rule of law."

The Ministry of Land, Infrastructure and Transport announced Thursday the results of a two-week survey of illegal activities at construction sites, saying 2,070 cases of wrongdoings, including solicitation of bribes, were reported at 1,489 sites nationwide.

On the previous day, the Korea Land and Housing Corp. said it had detected 270 illegal activities by the construction union, adding that they would ask police to investigate further and take civil and criminal action.

Moreover, the safe trucking freight rates system, which sparked the cargo union to strike last year, is now facing abolishment. The Ministry of Land, Infrastructure and Transport held a public hearing Wednesday and unveiled a plan to introduce a standard fare system for freight trucks, fading out the request of the cargo union.

This came just a day after the National Intelligence Service and police raided KCTU officials on alleged violations of the National Security Act.

The spy agency alleged that KCTU members had been in contact with North Korean agents overseas and received orders from them.