U2's concert scheduled for Saturday night in St. Louis has been cancelled because St. Louis police told the band they can't provide the usual level of security because of protests that have erupted in the city.

"We have been informed by the St. Louis Police Department that they are not in a position to provide the standard protection for our audience as would be expected for an event of this size," Live Nation and U2 said in a joint statement.

The statement added that because "local crowd security personnel would not be at full capacity," they "cannot in good conscience risk our fans' safety by proceeding with tonight's concert.

"As much as we regret having to cancel, we feel it is the only acceptable course of action in the current environment," the statement concludes.

Unrest has broken out in the St. Louis area following the acquittal of former St. Louis police officer Jason Stockley in the shooting death of Anthony Lamar Smith, a black male.

Protests began peacefully on Friday, but police say demonstrators threw rocks at the mayor's house and smashed the windshield of a police vehicle.

At least 23 people were arrested after officers had to use tear gas to disperse protestors.

"I will protect people's constitutional right to peacefully protest, but violence will not be tolerated. We will protect people's lives, homes, and communities," Missouri Gov. Eric Greitens said in a Facebook post.