Wai Moe Naing has been one of main members of an anti-coup protest organising group.
Myanmar security forces have arrested one of the main leaders of the campaign against military rule, Wai Moe Naing, as he led a motorbike protest rally in the central town of Monywa.
"Our brother Wai Moe Naing was arrested. His motorbike was hit by a private car of the police," Win Zaw Khiang, a member of a protest organising group, said on social media on Thursday.
Reuters was not able to contact Wai Moe Naing by telephone.
Earlier, Reuters spoke to him as he set off to lead the rally.
Monywa has been one of main centres of opposition to the military's February 1 coup and overthrow of an elected government led by Nobel laureate Aung San Suu Kyi.
READ MORE: Bloody protest in Myanmar marks lives lost to junta crackdown
Security forces open fire on medical workers
Myanmar security forces opened on Thursday fire on a pro-democracy protest by medical workers in the city of Mandalay, and during more shooting in a nearby area one man was killed and several were wounded, media reported.
Medical workers, some of whom have been at the forefront of the campaign against the coup, gathered in the second city of Mandalay early but troops soon arrived to disperse them, opening fire and detaining some people, the BBC's Burmese-language service said.
The BBC and other news outlets did not have details of casualties or arrests at the protest but Khit Thit media said a man was shot and killed in the compound of a nearby mosque as security forces broke up the medics' protest.
A spokesman for the junta could not be reached for comment.
A resident of the neighbourhood where the mosque is located said soldiers had arrived there and started shooting, wounding one person who was later taken to hospital.
"There was no protest here. The soldiers just came and seemed to be searching for someone," the resident, who declined to be identified, said by telephone. The BBC Burmese service reported four people were wounded in that neighborhood.
The five-day New Year holiday, known as Thingyan, began on Tuesday but pro-democracy activists cancelled the usual festivities to focus on their opposition to the generals.
Hundreds of people joined protests marches in several other towns, according to pictures posted by media outlets.
The coup has plunged Myanmar into crisis after 10 years of tentative steps toward democracy, with, in addition to the daily protests, strikes by workers in many sectors that have brought the economy to a standstill.
An activist group, the Assistance Association for Political Prisoners, says the security forces have killed 715 protesters since the ousting of Suu Kyi's government.
The United Nations human rights office said on Tuesday it feared the military clampdown on the protests risked escalating into a civil conflict, such as that in Syria.
READ MORE: Is Myanmar's army selling the bodies of protesters to their relatives?
The military says the protests are dwindling but the state-run Global New Light of Myanmar newspaper reported that "rioters" had been committing an increasing number of "terrorist acts", attacking the security forces with grenades and live ammunition, planting "homemade mines" in public places and starting fires.
"Action will be taken against those perpetrators as soon as possible according to the law," it said.
The coup has also led to an increase in clashes between the military and ethnic minority forces fighting for autonomy in border regions, in particular in the east and north, where the military has been launching air strikes.
Government forces had suffered heavy casualties in an assault on ethnic Kachin militia in the north this week, the Myanmar Now and Democratic Voice of Burma media groups reported.
State media reported that fighters from the Kachin Independence Army had extorted money from vehicles and set fire to four rice trucks on Tuesday and the army had mounted an operation in response.
Fighting in the are a has in the past sent villagers fleeing into China but there have been no reports of people seeking refuge on the Chinese side of the border this time.
In eastern Myanmar, fighting between the army and ethnic Karen insurgents has sent several thousand villagers fleeing into neighbouring Thailand and displaced many more internally, aid groups say.
The United States and other Western countries have imposed limited sanctions focused on the military in response to the coup. Southeast Asian neighbours have been encouraging talks between the rival sides in Myanmar without success.
The UN Security Council has called for the release of Suu Kyi and others but stopped short of condemning the coup.
READ MORE: Suu Kyi hit with another charge as Myanmar activists seek new year defiance