The U.K. terror threat level has been reduced to "severe" from "critical," Prime Minister Theresa May said in a televised statement. A "severe" threat level indicates that a terrorist attack is highly likely, she said.

The threat level was lowered following several arrests related to the May 22 suicide bombing in Manchester, according to a Bloomberg News report. A significant amount of police activity in the past 24 hours has occurred and 11 people are being held in custody, May said, according to the report.

The level had been raised to "critical" — its highest level, indicating an imminent attack — on May 23.