The military has ramped up its attempts to crush dissent following mass demonstrations against its ousting of civilian leader Aung San Suu Kyi, with at least 737 civilians killed and the press increasingly under attack.

Yuki Kitazumi was detained on Sunday, and a Japanese embassy spokesman confirmed that he was transferred overnight from a police watchhouse to the Insein prison.

Insein is notorious for holding political prisoners.

Japanese diplomats had sought permission to visit him in jail but that request had not yet been granted, an embassy spokesman told AFP on Monday.

"We are informed by the police he was arrested due to the suspicion of releasing fake news," he told AFP.

Myanmar authorities told the embassy the journalist was not physically harmed during the arrest and was in good health.

"We are asking Myanmar for the person's early release. We will do our utmost to protect the Japanese national," Japanese government spokesman Katsunobu Kato told reporters.

It is the second time Kitazumi has been detained since the coup. In February, he was beaten up and briefly held in custody during a crackdown on protesters but was later released.

The press has been caught in the junta's crackdown as the military attempts to tighten control over the flow of information, throttling internet access and revoking the licenses of five local media outlets.

Authorities in Myanmar have been charging journalists with a section of the country's penal code which criminalises spreading dissent and false news against the military.

Those convicted can face up to three years in jail.

At least 34 journalists and photographers remain in custody across Myanmar, according to monitoring group Reporting ASEAN.

- 'Guerrilla war' -

The central city of Myingyan has seen fighting between residents and the military for two days.

At least four people were shot on Monday afternoon, a resident told AFP, adding that one of the wounded had been unable to receive medical treatment.

It was unclear how many people died at Myingyan.

"There is still some shooting. It's like guerrilla war in our town," the resident told AFP, adding that people were trying to defend themselves with homemade guns.

"The army did not allow anyone to be on the street. They shoot anyone they see on the street. They tried to check house by house to arrest protesters."

The resident said the military set fire to some residents' motorbikes.

At least six people including a 13-year-old have been arrested in Myingyan, local media reported.

- Pot-banging sailors -

Meanwhile, close to 40 Myanmar sailors in hotel quarantine in Yangon had security forces barge into their rooms on Sunday after some of them participated in the daily protest ritual of banging on pots and pans.

Traditionally a way for Myanmar people to drive away evil spirits, the activity has become an act of resistance since the putsch, with nightly drumming from 8 pm local time.

The seafarers were staying at the Hlaine Tet Hotel after returning from South Korea.

Myo Min, who did not use his real name, said his group was beaten up and that some were robbed -- one seafarer's $1,500 salary was stolen.

Three were badly injured, he added.

"As soon as the door was opened, they started beating us," he told AFP, by phone.

"None of them were wearing masks... It is totally unacceptable. I felt insecure now. I just want to go back home. No one can protect us."