South Korean police say they've arrested four people on suspicion of secretly filming about 1,600 guests in hotel rooms and posting or streaming the footage on the internet.

The Korean National Police Agency said Thursday the four men are accused of installing mini-spy cameras in TV set-top boxes, hair dryers or electrical outlets in 42 rooms in 30 hotels throughout South Korea.

A police statement accused the men of earning about 7 million ($6,210) in total by posting or livestreaming the footage on an internet site they opened late last year.

The illicit distribution of video taken by hidden cameras is a serious social problem in South Korea. Thousands of women rallied in Seoul several times last year, demanding stronger government measures against the spread of such videos.