Growing fighting between Myanmar's army and ethnic Kokang fighters in a region bordering China has killed dozens in the past week and sent tens of thousands fleeing across the frontier, reports said Monday.

China warned of a threat to border stability after the dramatic upsurge in conflict in a remote region in Myanmar's northeastern state of Shan.

Beijing's official Xinhua news agency said there had been more than 30,000 crossings into Yunnan province in the past week.

"Residents from Myanmar have crossed into China more than 30,000 times since Feb. 9," the press office of Yunnan's Lincang City said in a statement quoted by the agency.

"The Chinese side provided necessary aid and supplies ... offering them food, medicine and quarantine services."

Urging both sides to "exercise restraint", Chinese foreign ministry spokeswoman Hua Chunying said in Beijing that more fighting "will have an impact on the stability of the China-Myanmar border areas and the security on the Chinese side of the border".

Hua said China respects Myanmar's "territorial integrity" and vowed it "will not allow any organisation or individual to carry out activities undermining China-Myanmar relations... (from) within Chinese territory."

Myanmar authorities have blamed local Kokang rebel leader Phone Kya Shin for the fighting, and called on Beijing to rein in any local officials who might be helping the group on its side of the border.

In a statement late Monday the Myanmar government said it would "continue to perform actions in the Kokang region that are necessary for the safety and security of local people, as well as peace, stability and the rule of law".

Nearly 2,000 people have fled the area for central Myanmar, according to a report in state-backed media on Monday.

In addition to ground fighting the Myanmar military has launched airstrikes against rebels who tried to capture Kokang's main town of Laukkai.

Unrest flared in Kokang on February 9, shattering nearly six years of relative calm, in a blow to Myanmar's quasi-civilian government as it tries to end the country's myriad ethnic minority conflicts.

Details of the fighting in the remote mountainous region remain difficult to confirm.

In 2009 more than 30,000 people flooded over the border into China as Myanmar's army launched an offensive against Kokang rebels.

The fighting earned Myanmar's then-junta a rare rebuke from China, the country's powerful northern neighbour which at the time was almost its sole ally on the international stage.

The Global New Light of Myanmar on Monday reported that eight captured Kokang rebels had "died of their wounds" in custody, while a further 18 others had been killed in recent fighting.

Myanmar's military last week said 47 of its own soldiers had been killed and dozens more injured in the first few days of the conflict, in unusually candid reports of casualty numbers.

Observers say this approach may be an attempt to drum up sympathy for government soldiers in the former army-run nation, and justify a severe crackdown on the rebels.

The Kokang have been joined by the Ta'ang National Liberation Army and the powerful Kachin Independence Army, which have both continued to battle government forces in other areas of Shan and in nearby Kachin state.

Despite the latest flare-up the government, military and a handful of ethnic armed groups signed a commitment Thursday to continue talks with the aim of building a union with "federal principles".

But a long hoped-for nationwide agreement to end the civil wars that have plagued Myanmar since independence in 1948 remains elusive.