(Reuters) - The acting leader of Myanmar's parallel civilian government said it will seek to give people the legal right to defend themselves as the death toll in protests against last month's coup exceeded 80, according to an advocacy group.

Mahn Win Khaing Than, who is on the run along with most senior officials from the ruling National League for Democracy Party, addressed the public via Facebook, saying, "This is the darkest moment of the nation and the moment that the dawn is close".

He said the civilian government would "attempt to legislate the required laws so that the people have the right to defend themselves" against the military crackdown.

More than 80 people had been killed as of Saturday in widespread protests against the military's seizure of power, the Assistance Association for Political Prisoners advocacy group said. Over 2,100 people have been arrested, it said.

At least 13 people were killed on Saturday, one of the bloodiest days since the Feb. 1 coup, witnesses and domestic media said.

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.

Two people were 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 in a war zone, with unarmed people," said Mandalay-based activist Myat Thu. He said the dead included a 13-year-old child.

Si Thu Tun, another protester, said he saw two people shot, including a Buddhist monk. "One of them was hit in the pubic bone, another was shot to death terribly," he said.

A truck driver in Chauk, a town in the central Magwe Region, died after being shot in the chest by police, a family friend said.

A spokesman for the junta did not answer phone calls from Reuters seeking comment. Junta-run media MRTV's evening news broadcast labelled the protesters "criminals" but did not elaborate.

PROTESTS

Saturday's protests erupted after posters spread on social media urging people to mark the death anniversary of Phone Maw, who was shot and killed by security forces in 1988 inside what was then known as the Rangoon Institute of Technology campus.

His shooting and that of another student who died a few weeks later sparked widespread protests against the military government known as the 8-8-88 campaign, because they peaked in August that year. An estimated 3,000 people were killed when the army crushed the uprising.

Aung San Suu Kyi emerged as a democracy icon during the movement and was kept under house arrest for nearly two decades.

She was released in 2010 as the military began democratic reforms. Her National League for Democracy won elections in 2015 and again in November last year.

This year, the generals overthrew her government and detained Suu Kyi and many of her cabinet colleagues, claiming fraud in the November elections.