The South Korean spy agency and police raided the headquarters of a major umbrella labor union in central Seoul on Wednesday morning, on suspicion that some members had violated national security laws.

The National Intelligence Service said it obtained a search and seizure warrant from the court for the Korean Confederation of Trade Unions on charges of violating the National Security Act, an NIS official confirmed to The Korea Herald on condition of anonymity Wednesday.

"The NIS has been conducting a joint investigation with the police into the suspects on charges of violating the National Security Act," the NIS official said. "After years of internal investigations into the suspects' alleged links to North Korea, the NIS has concluded that compulsory investigation is necessary. And therefore, we requested a search warrant," the official added, declining to share further details.

Investigators from the NIS and National Police Agency attempted to search the office of KCTU in Jung-gu, central Seoul, from 9:10 a.m.

KCTU officials confronted the investigators, demanding that to proceed with the presence of a lawyer. The confrontation lasted about three hours, and the mayhem was shared in real time through the KCTU’s official YouTube channel under the title “Emergency Live Broadcast.”

But investigators pushed into the office, citing the risk of destruction of evidence, and they were able to launch their raid on the headquarters at around noon.

Beyond the KCTU Seoul headquarters, the NIS and police simultaneously raided several other locations across the country, including the office of the Korean Health and Medical Workers’ Union located in Yeongdeungpo-gu, Seoul, and the houses of union members suspected of violating the National Security Act.

The NIS is reportedly investigating allegations that officials related to the KCTU have been in contact with North Korean agents overseas, possibly in Cambodia and Vietnam, and received orders from them.

Han Sang-jin, a spokesperson for the KCTU, confirmed that total four members of the union -- from the KCTU leadership, medical workers' union, Kia Motor workers' union in Gwangju and Jeju Sewol Ferry Memorial, respectively -- were targets of the raid.

Han also explained that this is the first time that the NIS has raided the KCTU headquarters on charges of violating the National Security Act.

Police said that the search and seizure was conducted on individual members of the KCTU on charges of violating the National Security Act, not the entire organization.

Police also denied that the raid is connected with cases concerning a spy organization the NIS has recently been investigating. The NIS recently expanded a probe into an alleged spy organization involving progressive political and labor figures on Jeju Island and in South Gyeongsang Province.

However, Han claimed the raid appeared to be an attempt to forcefully link the spy ring with the KCTU by holding a press briefing at around 11 a.m. in front of the building where the union headquarters is located.

"We don't have much reason to block or resist the raid. But they seek to create a scene by deploying hundreds of police personnel and even brought air mattresses," Han told media during a press conference, saying that the NIS and police "unreasonably and forcibly" executed their search warrant.

Han raised further suspicions about hidden intentions behind the raid, claiming that several crises related to the ruling party and the Yoon administration faded out from the press afterward.

"Stories of President Yoon Suk Yeol's slip of the tongue during his trip to the United Arab Emirates, the end of the Itaewon disaster investigation with a report only opposition party participated, and dispute related to the ruling party leader election, all of this disappeared from the paper and broadcast because of the seizure and search today," said Han, implying that it was not a coincidence.