Myanmar rebels Saturday said the national army had launched fresh air strikes following the government's rare admission that dozens of its soldiers had died in a dramatic resurgence of conflict in a remote region bordering China.

Unrest in Kokang, Shan State, which erupted on February 9 after six years of relative calm, continued on Friday with severe clashes between fighters from several ethnic groups and the Myanmar army, according to Captain Tar Parn La, a spokesman for the Ta'ang National Liberation Army (TNLA).

"There were gunships, two jets and two helicopters yesterday," he told AFP, adding that he had not yet received reports of fighting on Saturday.

Myanmar state media on Friday reported that ethnic minority fighters armed with heavy weapons had attempted to capture the Kokang's main city earlier in the week in a series of assaults that have left at least 50 soldiers dead and dozens more wounded.

It said the army had used airstrikes to repel the attacks, which have come as a blow to the quasi-civilian regime as it looks to ink a historic nationwide ceasefire to end the country's myriad ethnic minority conflicts.

Myanmar's information minister Ye Htut has blamed local Kokang rebel leader Phone Kya Shin for the fighting and called on Beijing to reign in any local officials who might be helping the group on their side of the border.

An unknown number of people have fled the Kokang unrest, with most crossing the border into China, while some have made their way to the northern Shan city of Lashio, according to Tar Parn La.

He said the Kokang rebels have been joined by the TNLA and the powerful Kachin Independence Army (KIA), which have both continued to battle the government's forces in other areas of Shan and nearby Kachin states.

But he said he was unaware of involvement by China, which has called for a peaceful resolution to the conflict.

It is unclear what provoked the latest round of violence, which coincided with the country's celebrations of its symbolic Union Day Thursday.

The government, the military and a handful of ethnic armed groups signed a commitment to continue talks, laying out an aim to build a union with "federal principles", but a long hoped for nationwide ceasefire deal remains elusive.

Fighting in resource-rich Kachin, which erupted in 2011 when a 17-year ceasefire crumbled, is seen as a significant barrier to reaching an agreement. It has seen some 100,000 people forced into displacement camps.