Eleven Chinese and Russian military aircraft entered South Korea's air defence identification zone on Friday over a period of four hours, prompting South Korea to launch fighter jets, South Korea's military said.

South Korea's military said Friday it scrambled fighter jets as five Chinese and six Russian military planes flew through its air defence zone, an area wider than the country's airspace.

The staff have been instructed to leave Lithuania within a week, the ministry said in a statement, exacerbating sour relations between the two countries. China's representative office in Lithuania could not be immediately reached for comment.

Lithuania said on Friday it was expelling three Chinese embassy staff as ties between the Baltic country and Beijing fray over Taiwan support and the suspected involvement of a Chinese ship in sea cables damage.