MYANMAR security forces killed at least 12 people, witnesses and media reported, as the acting leader of a civilian parallel government vowed in a first public address on Saturday to pursue a "revolution" to overturn the February 1 military coup. Five people were shot dead and several injured when police opened fire on a sit-in protest in Mandalay, Myanmar's second-biggest city, witnesses told Reuters. Another person was killed in the central town of Pyay and two died in police firing in the commercial capital Yangon, where three were also killed overnight, domestic media reported. "They are acting like they are…