Photo/IllutrationA police officer demonstrates mini-spy cameras installed in a hair dryer and shown on a screen, center rear, at a police station in Seoul on March 20. (Yonhap via AP)

SEOUL--South Korean police said Thursday 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 mini-spy cameras were set up 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 won ($6,210) in total by posting or livestreaming the footage on an overseas-based Internet site they opened late last year.

If convicted, the two main culprits could each face up to seven years in prison, according to police.

One of the main culprits allegedly installed the cameras after entering the hotels as a guest. The other was accused of being responsible for launching and managing the now-shuttered website. The other two were allegedly involved in buying the spy cameras or funding the Internet site's operation, according to police.

Police said it's the first South Korean arrest for livestreaming the private lives of hotel guests via an overseas-based website.

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.

In a separate case, a Seoul district court was reviewing whether to issue an arrest warrant for a K-pop singer on allegations he secretly filmed himself having sex with women and then shared the videos with friends in mobile group chats.