MAE SAM LAEP: About a dozen people fleeing military air strikes in Myanmar were allowed to cross into a Thai border village on Tuesday to receive medical treatment, as Thailand's prime minister said authorities had asked others who fled to return.

Thailand has been accused by activists of pushing back thousands of people trying to flee violence against those opposing Myanmar's military coup in February, an accusation the foreign ministry has denied.

A health official in Mae Sam Laep village said the people who arrived by boat across Salween river marking the border were ethnic Karen who were wounded in violence.

However, the Thai army was still sending back most of those fleeing Myanmar because it had deemed the situation over the border to be safe, another official in the area, who spoke on condition of anonymity, told Reuters.

On Tuesday, Myanmar villager Kyaw Lar Bri, 48, said he was hit by bomb shrapnel from an air attack on Saturday before fleeing into the jungle and later boarding a boat to cross the river to Mae Sam Laep along with six other wounded people.

"It is still not safe and villagers do not dare to return to the villages," he said.

Another woman who was receiving treatment in Thailand appeared to have scarring and blisters on her face.

Activists on Monday accused Thailand of pushing thousands back into Myanmar, releasing video published by Reuters of people boarding boats on a riverbank under the watch of Thai soldiers.

Thai Prime Minister Prayuth Chan-ocha on Tuesday downplayed the situation at the border.

"Some villagers arrived and we asked what problems there were and they said they weren't (any) - then can you go back first? We didn't point guns in their faces, we even wished each other well. That's humanitarian," Prayuth said.

"If there is real suffering, we can't deny them. We are not making an announcement welcoming them - that's not it," he said.

Thailand's Foreign Minister Don Pramudwinai said his country had asked Myanmar's new military rulers to reduce the level of violence after security forces on Saturday killed at least 141 people opposing the coup.

Heavy clashes erupted on the weekend near the Thai border between the army and fighters from Myanmar's oldest ethnic minority force, the Karen National Union (KNU), which has also denounced the coup.

The KNU was warning of further attacks, saying it had intelligence that its headquarters at Laywah, where people fleeing central areas are believed to be sheltering, would be bombed. A source from the group said fighter jets had been flying over the area on Tuesday.

People from Myanmar have also being trying to cross into India, where a border state withdrew an order to refuse food and shelter to people from Myanmar fleeing bloodshed, according to two officials, after the measure drew fierce public criticism.