SEOUL, South Korea — Thousands of South Korean women gathered in Seoul on Saturday to demand stronger government action to fight the spread of intimate photos and footage taken by hidden cameras, which they say has women living in constant anxiety and distress.

Police said about 18,000 took part in the all-women protest, with demonstrators calling for stronger investigations and punishments against male offenders who photograph or film women without their knowledge and post the material online.

Most of the protesters covered their faces with baseball caps, sunglasses and surgical masks as instructed by organizers, who intended to make a statement against an environment in which women constantly worry about tiny cameras hidden in bathrooms or being filmed from under their skirts at subway stations. However, there was also criticism about the organizers' tight control over the protests and the decision to block the participation of those who weren't "biologically women."

Protesters, many of them wearing red T-shirts with signs that read "Angry women will change the world," roared in support as two women volunteered to have their heads shaved on a stage.

"Let's fight until the last seed of illicit filming dies!" one protester shouted into the microphone while another shaved off her hair. "Here's my message to men: I am not an object of our sexual desires! I am a first-rate citizen, just like you!"

Female protesters call for South Korea's government to crack down on widespread spycam porn crimes during a rally in Seoul on July 7, 2018. AFP - Getty Images

South Korea has struggled over the years to deal with perpetrators who use tiny cameras or smartphones to film under women's clothing to see their genitals or underwear. The footage is heavily circulated on illicit porn sites, such as Soranet, which had more than a million users before police managed to shut it down in 2016. An unknown number of similar sites are still running.

Since 2004, South Korea has required smartphones to make large shutter sounds when taking pictures and videos to prevent such crimes. However, phone cameras can be silenced through apps and there's also an abundance of miniaturized cameras that can be hidden inside bags, shoes and toilets or small holes drilled into bathroom walls and doors.

Amid rising criticism, South Korean President Moon Jae-in on Tuesday ordered government officials to explore tougher punishments for hidden-camera crimes and also ensure that the perpetrators' actions are immediately notified to employers.

"We must make sure that the offenders suffer greater damage than the damage they inflict," Moon said in a Cabinet meeting.

The national government plans to spend 5 billion won ($4.5 million) to equip local governments with more camera detecting equipment and strengthen inspections of bathrooms in public spaces and private buildings. There are also plans to widen inspections to elementary, middle and high schools.

Under South Korean law, creating intimate sexual images without consent is punishable by a prison term of up to five years or a fine of up to 10 million won ($8,900). Distributing such images for the purpose of profit is punishable by up to seven years in prison or a 30 million won ($27,000) fine.

Saturday's gathering in Seoul was a follow-up to large protests by women in May and June over the proliferation of hidden-camera images as pornographic material.

The protests were sparked by the arrest of a 25-year-old woman in May who was found to have secretly taken a photo of a male colleague while he posed nude for university art students and uploaded it online.

The swift investigation struck a nerve among many women who questioned whether the police care about the hidden-camera issue only in rare instances in which the victim is male. Protesters pointed to countless cases involving female victims that were closed because the police were unable to track down the perpetrators or porn sites based on foreign servers. The National Police Agency had denied that officers treat cases involving male victims more seriously.