TAIPEI, Taiwan (AP) — Taiwan has detained an army officer and several collaborators on suspicion of handing military secrets to China.

The defense ministry said Wednesday that a lieutenant colonel surnamed Hsieh and other defendants were suspected of having been recruited by China to leak national defense secrets and other information.

The detentions come as military tensions between China and Taiwan continue to rise. China claims self-ruled Taiwan as its own territory and has run a long-standing campaign to recruit retired Taiwanese military personnel to supply state secrets in exchange for money or gifts.

Hsieh is also suspected of developing a spy organization of current and retired military personnel tasked with collecting intelligence for China, according to the Taipei Times newspaper, which quoted unnamed prosecutors with Taiwan’s High Prosecutors Office.

The office did not immediately answer emailed questions about the case.

“The Ministry of National Defense is saddened and severely condemns the small number of unscrupulous people who violated the duty of defending the country and committed such crimes as betraying the people of the country,” the defense ministry said in a statement.

A retired army major and three other people have also been questioned in the case and released on bail between 20,000 New Taiwan Dollars ($630) and 600,000 New Taiwan Dollars ($19,000), according to the Taipei Times.

Last month, Taiwanese authorities detained five people, including a Chinese yo-yo instructor, on suspicion of spying for China.