The foreign ministry in Tokyo on Friday proposed a meeting with Chinese officials about the choking smog over Beijing that is now being seen in Japan.

The ministry told China "the Japanese government is concerned and is closely monitoring the recent serious air pollution in China" as it may affect Japan's environment as well as Japanese nationals in the country, a statement said.

Tokyo proposed that the countries hold talks as soon as the Chinese New Year holiday season ends this month, to discuss how the two parties can cooperate over the problem.

The suffocating smog that has blanketed swathes of China is hitting parts of Japan, sparking warnings of health risks for the young and the sick.

Relations between Tokyo and Beijing are already strained over the sovereignty of a chain of islands in the East China Sea.

That dispute intensified further this week after Japan alleged a Chinese warship's radar system had locked onto a Japanese destroyer.

Beijing on Friday accused Tokyo of hyping the "China threat".

While the island spat has hit a number of Japanese businesses amid an informal boycott of Japanese brand goods, the elevated pollution levels in China have been good for Japan's air purifier makers.

Sharp, Daikin and Panasonic all said sales in China for January were up two or three times on the same month last year.