BEIJING, March 14 (Xinhua) -- China's Air Force sent fighter jets to patrol over the China-Myanmar border after four Chinese were killed by a bomb dropped by a Myanmar warplane in southwestern Yunnan Province, a military spokesman said Saturday.

The People's Liberation Army Air Force dispatched several batches of fighter jets on Friday to "track, monitor, warn and chase away" Myanmar military planes flying close to the Chinese border, said Air Force spokesman Shen Jinke.

The Air Force have been always on high alert, kept close watch on the air situation and strengthened surveillance over the China-Myanmar border recently, said Colonel Shen.

He said the Air Force will take measures to enhance response over the China-Myanmar border in order to "safeguard sovereignty of the national territorial air space."

Chinese Vice Foreign Minister Liu Zhenmin summoned Myanmar ambassador Thit Linn Ohn in Beijing Friday night, lodging solemn representations to him after the bomb hit a sugarcane field in the border city of Lincang and killed four people working there on Friday afternoon. Nine others were also injured.

Earlier this week, the Chinese foreign ministry said that stray fire from a fight that occurred on Sunday between Myanmar's government forces and a local ethnic army had damaged a house in China.

On Friday, Liu condemned the incident in the sugarcane field and urged the Myanmar side to thoroughly investigate the case and inform the Chinese side of the result.

He also urged the Myanmar side to punish the perpetrator, appropriately handle the aftermath, and take immediate and effective measures to prevent recurrence of such incidents and safeguard the security and stability in the border areas between China and Myanmar.