The death toll from crackdowns on anti-coup protests by Myanmar's military had reached 320 by Thursday night, a rights group monitoring the situation said, while the outside world has found few effective means to rein in the indiscriminate violence against citizens.

There is a growing concern that the military may intensify its crackdown with a military parade scheduled for Armed Forces Day on Saturday, which is considered the most important event for the military.

Meanwhile, the military released Friday over 300 people who had been detained by security forces, including protesters. It is unclear on what grounds they were released, but some have speculated that the move may be aimed at appeasing the public ahead of the military parade.

Save the Children, a nongovernmental group, said more than 20 children have been killed since the military seized power in a coup on Feb. 1, including a 7-year-old girl who was shot dead at her home on Tuesday in the country's second-largest city Mandalay.

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She has become the youngest victim of the crackdowns.

In Mandalay on Monday, a 14-year-old boy was reportedly killed in an assault by soldiers while he was at home.

"Even staying in your home is not secure," Ko Bo Kyi, co-secretary of the rights group Assistance Association for Political Prisoners, said on Twitter, adding that the Mandalay girl was killed "intentionally...not accidentally."

The more than 300 detainees left a prison in the suburbs of the country's largest city Yangon in six buses on Friday. The mass release came two days after the military released about 630 detainees.

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The military ousted the elected government led by Aung San Suu Kyi, alleging widespread voter fraud in last November's general election, which was won resoundingly by her National League for Democracy party.

The military has been keeping Suu Kyi and other prominent politicians in detention.