Images showed bodies lying in pools of blood on the streets, the injured frantically carried away with bullet wounds peppering their limbs, and protesters huddled behind makeshift shields and barricades, as Myanmar's security forces Sunday launched their most violent and deadly crackdown on peaceful demonstrators since the February 1 coup, CNN reports.

At least 18 people died and more than 30 were injured, according to the United Nations Human Rights Office, as police attempted to extinguish a month-long nationwide protest movement against the military coup which ousted the democratically elected government of civilian leader Aung San Suu Kyi. Activist groups have put the death toll and number of injured as higher.

In one image that was shared widely on social media, a nun in northern Kachin state -- her hands raised -- knelt on the ground and pleaded with a line of riot police to stop arresting protesters.

Before Sunday, protests had seen sporadic violence in some areas but there appeared to be a coordinated change of tack from security forces across the country, who opened fire on protesters, used tear gas, flash bangs and stun grenades in towns and cities.