Supporters and opponents of Myanmar's military have clashed on the streets of Yangon as authorities blocked students from leaving their campus for a protest march.
The country has been in turmoil since the army seized power on February 1 and detained civilian government leader Aung San Suu Kyi and much of her party leadership, alleging fraud in her election victory in November.
There have been about three weeks of daily protests and strikes and students pledged to come out again in the commercial hub of Yangon on Thursday.
But police blocked the gates of the campus, stopping hundreds of students inside from coming out to march.
At the same time, about 1,000 supporters of the military gathered for a rally in central Yangon.
Some of them threatened news photographers, media workers said, and scuffles broke out between the pro- and anti-military demonstrators. One photographer was slightly hurt, he said.
Later, military supporters threw stones and fired catapults, witnesses said, and there was an unconfirmed report of a stabbing.
The confrontation underscored the volatility in a country largely paralysed by protests and a civil disobedience campaign of strikes against the military, which many professionals and government workers have joined.
Doctors were due to hold a protest on Thursday as part of a so-called white coat revolution.
Meanwhile, Facebook said it had banned the Myanmar military from using it and its Instagram platform with immediate effect. It cited violence and the risk of letting the military use the platforms.
Military chief General Min Aung Hlaing says authorities are following a democratic path in dealing with the protests and police are using minimal force, such as rubber bullets, state media reported.
Nonetheless, three protesters and one policeman have been killed in violence.
A rights group said as of Wednesday 728 people had been arrested, charged or sentenced in relation to the pro-democracy protests.
Suu Kyi has been detained incommunicado since the coup, at her home in the capital, Naypyitaw, but her party says its November victory must be respected.
The question of an election has emerged at the centre of regional diplomatic efforts to find a path out of the crisis, with Indonesia taking the lead within the Association of Southeast Asian Nations.
Its foreign minister Retno Marsudi met Myanmar's military-appointed foreign minister, Wunna Maung Lwin, for talks in the Thai capital on Wednesday.
Indonesia's intervention has raised fears among coup opponents that it will confer legitimacy on the junta and its bid to scrap the November election.
Retno told reporters the wellbeing of the people of Myanmar was the top priority.
"We ask for everybody to use restraint and not resort to violence," she said after talks with the Myanmar minister and her Thai counterpart, Don Pramudwinai.
Retno emphasised "the importance of an inclusive democratic transition process".
Wider international concern is also growing, with the United States, Britain and others imposing limited sanctions aimed at members of the junta and military businesses.
Australian Associated Press