Myanmar security forces opened fire on pro-democracy protests on Saturday killing at least five people, a protester and media said, as the military stepped up its bid to stifle dissent with arrest warrants for a further 20 high-profile critics.

Despite the killing of more than 550 people by the security forces since the Feb. 1 coup, protesters are coming out every day, often in small groups in small towns, to voice opposition to the overthrow of an elected government led by Aung San Suu Kyi and the return of military rule...