Doha: South Korean police on Tuesday raided the country's spy agency and a military intelligence command and booked three active-duty military officers as suspects in connection with alleged drone flights into North Korea.

According to Qatar News Agency, a joint team of police and military investigators carried out search and seizure operations at the National Intelligence Service and the Defense Intelligence Command, as well as 16 other locations, including the homes and offices of the suspects, Yonhap reported.

The three officers -- including a major and a captain assigned to the military intelligence unit -- are suspected of involvement in the alleged drone incursions. Authorities did not disclose further details of their specific roles, citing the ongoing investigation.

The joint probe was launched last month after North Korea accused South Korea of violating its sovereignty by flying drones into its territory in September and again on January 4.

Investigators had initially focused on three civilian suspects, including a graduate student in his 30s who claimed responsibility for the drone flights. Subsequent inquiries, however, uncovered alleged links between the civilian suspect and the military intelligence unit, prompting the investigation to expand.

Earlier this year, Pyongyang accused Seoul of flying a drone into the city of Kaesong, releasing images that it said showed debris from a downed unmanned aircraft. South Korean authorities have so far declined to publicly confirm or deny the allegations.