SHANGHAI - China has summoned the Myanmar ambassador for a meeting in Beijing after a bomb from a Myanmar aircraft fell in Chinese territory and killed four Chinese people, China's foreign ministry said on Saturday.
Myanmar government forces have been battling rebels on the border with China since last month and China has urged Myanmar to "lower the temperature".
But Myanmar denied that any bomb from its forces had fallen in China and said the rebels might have fired into China to create "misunderstanding".
China said the bomb from the Myanmar aircraft fell on Friday in a sugarcane field near the city of Lincang, in the southwestern Chinese province of Yunnan. Nine people were wounded, state media reported.
The incident came days after a stray shell from Myanmar flattened a house in Chinese territory, prompting condemnation from Beijing.
Tens of thousands of people, many of them ethnic Chinese, have fled the fighting in northeastern Myanmar's Kokang region into China.
Chinese Vice Foreign Minister Liu Zhenmin urged the Myanmar ambassador, Thit Linn Ohn, to investigate the aircraft bombing and to take steps to ensure the safety of the border area.
A spokesman for China's air force said it had dispatched aircraft to patrol the border and step up the protection of China's airspace, the Defence Ministry said.
An official in the office of the Myanmar president said Myanmar forces had kept Chinese forces fully informed of their air operations, which were carried out "strictly adhering to the information we told them".
"The targets of all our aerial attacks were inside our territory," the official, Zaw Htay, told Reuters.
"It's possible that those fighting with us purposely created these attacks with the intent of causing misunderstanding between China and us ... We plan to explain it to Chinese diplomats after summoning them."
Myanmar has said Chinese mercenaries were fighting with the rebels, and it has urged China to cooperate to prevent "terrorist attacks" being launched from Chinese territory.
China has denied that any attacks into Myanmar have been launched from its territory.
The rebels are from a group called the Myanmar National Democratic Alliance Army, which is led by ethnic Chinese commander Peng Jiasheng.
The MNDAA was formed from remnants of the Communist Party of Burma, a powerful China-backed guerrilla force that battled the Myanmar government until it splintered in 1989.
The group struck a truce with the government which lasted until 2009, when government troops took over their region in a conflict that pushed tens of thousands of refugees into China.
While the ethnic Chinese rebels have won some sympathy among the public in China, the Myanmar army, long feared at home for its suppression of democracy, has won favour from the Myanmar public for being seen to stand up to what many see as Chinese designs on Myanmar territory.
China and Myanmar share a 2,000 km (1,250 mile) border.