Fighting between Myanmar's isolated ruling junta and rebel ethnic armies in the remote northeast has driven up to 30,000 refugees into China, the UN said, as analysts warned of a full-scale civil war.
As thousands fled across its border, China issued a rare admonishment to its southern neighbour and close ally, urging it to resolve the conflict that has broken out in Kokang, a mainly ethnic Chinese region of Myanmar's Shan state.
A battle between the Kokang rebel group and the government's army began on Thursday in violation of a 20-year ceasefire, according to the US Campaign for Burma (USCB), which uses Myanmar's former name.
The mass exodus began after Myanmar's junta deployed troops in the region on August 8 and now "only elderly peoples are left at homes", while at least one Myanmar policeman was reportedly killed during the battle, the USCB added.
The United Nations Refugee Agency (UNHCR), which is liaising with local Chinese authorities on the displaced people's needs, said up to 30,000 crossed into the Chinese border town of Nansan, in southwestern Yunnan province.
"We have been informed that local authorities in Yunnan province have already provided emergency shelter, food and medical care to the refugees," UNHCR spokesman Andrej Mahecic said.
A statement from the Chinese foreign ministry said it "hopes that Myanmar can appropriately solve its relevant internal problems and safeguard the stability of the China-Myanmar border".
"We also urge Myanmar to protect the safety and legal rights of Chinese citizens in Myanmar," said spokeswoman Jiang Yu in the statement, posted on the ministry's website.
China is Myanmar's main source of military hardware and a major consumer of its vast natural resources, despite Western concerns over the military-ruled nation's rights record.
Chinese state media reported Friday that Beijing had increased its number of armed police along the Myanmar border.
The English-language Global Times, citing local officials, said that Myanmar nationals were still crossing the border into Yunnan province, without giving a specific figure.
Another ethnic group, the United Wa State Army, has now reportedly joined the Kokang forces' fight against the Myanmar junta, according to Khuensai Jaiyen, editor of the Shan Herald Agency for News.