SALT LAKE CITY, the United States, March 24 (Xinhua) -- Facebook, Twitter, Instagram and other social media platforms were muzzled Thursday when Utah became the first U.S. state to sign into law restrictions on social media's access to millions of children.

"We're no longer willing to let social media companies continue to harm the mental health of our youth," Utah Governor Spencer Cox said on Twitter.

"It is the first state law in the nation that will prohibit social media services from allowing users under 18 to have accounts without the explicit consent of a parent or guardian," the New York Times said.

Cox signed "sweeping legislation" in the state capital Thursday that "aims to limit when and where children can use social media and stop companies from luring kids to the sites," according to the Associated Press.

One clause requires social networks to give Utah parents "access to their children's posts, messages and responses," which experts said would likely be challenged by advocates of the First Amendment.

The new laws, slated to take effect on March 1, 2024, will require social media services to block Utah minors from accessing their accounts from local time 10:30 p.m. to 6:30 a.m., a setting that only a parent or guardian will be able to change.

The Utah Legislature passed the measures earlier this month, despite opposition from tech industry groups and civil liberties experts, according to the Times.

The conservative, Republican-dominated Utah legislature has prioritized mental health as one of many concerns expressed in ongoing debates about social media's impact on children's well-being.

Across the country, other states are responding to national concerns regarding social media and its access to minors. Last year, California enacted a sweeping online safety law requiring such services to turn on the highest privacy settings by default for users under 18.

It also requires social networks and other services to turn off features by default that could pose risks to younger people, like "friend finders" that allow adult strangers to contact children.