The United Nations Office for the Coordination of Humanitarian Affairs (OCHA), said relief operations were ongoing but were being hindered by armed clashes, violence and insecurity in the country.
It said 177,000 people were displaced in Karen state bordering Thailand, 103,000 in the past month, while more than 20,000 people were sheltering at 100 displacement areas after fighting between People's Defense Forces and the army in Chin State bordering India.
Several thousand people had fled fighting in northern Kachin and Shan States, regions with established ethnic minority armies with a long history of hostilities with the military.
The Karen National Union (KNU), one of Myanmar's oldest ethnic minority groups, said it was worried about the military's excessive use of force and the loss of innocent civilian lives as fighting intensifies all over the country.
"The KNU will continue to fight against military dictatorship and provide as much protection as possible to people and unarmed civilians," it said in a statement.
Protests across Myanmar
Anti-junta protests took place in Kachin state, Dawei, Sagaing region and the commercial capital, Yangon, on Thursday, with demonstrators carrying banners and making three-finger gestures of defiance.
Some showed support for those resisting military rule in Mandalay, the second-biggest city, where a firefight took place between the army and a newly formed guerrilla group on Tuesday, the first sign of armed clashes in a major urban center since the coup.
The military-owned Myawaddy Television said four members of the militia were arrested on Thursday, describing them as "terrorists".
At least 877 people have been killed by security forces and more than 6,000 arrested since the coup, according to the Association for Political Prisoners (AAPP), an advocacy group which the junta has declared an illegal organization.
A diplomatic effort by Southeast Asian countries to halt the violence and initiate dialogue between all sides has stalled and the generals say they will stick to their plan of restoring order and holding elections in two years.
In its nightly news bulletin, state-run MRTV reported on the visit of junta leader Gen. Min Aung Hlaing to Russia, where a military university named him an honorary professor.
Unlike most global powers, Russia has embraced the junta and the country has long been a key source of Myanmar's weaponry. His visit comes amid international pressure on countries not to sell arms to the military or do business with its vast network of companies.
State media on Thursday carried excerpts from a speech in Russia by Min Aung Hlaing in which he said it was necessary for countries to avoid encroaching on another nation's sovereignty.
"Myanmar is striving for restoring political peace and stability," it quoted him saying. "The current government is focusing on the reappearance of honesty over democracy."