Myanmar has sentenced an unspecified number of Chinese nationals to more than a decade in jail for illegal logging, China's state media reported Thursday, with Beijing's foreign ministry saying it was "highly concerned".

The loggers were arrested following a January crackdown on illegal forestry activities in Myanmar's northern Kachin state and sentenced to "more than 10 years in prison", state news agency Xinhua said.

An unnamed Myanmar court official in Kachin state told AFP on Wednesday that 153 Chinese loggers had been jailed for life for illegal logging. Xinhua's report did not specify the number of people imprisoned nor the exact sentences.

"Right after the Myanmar side arrested and detained some Chinese engaged in illegal logging in Myanmar early this year, the Chinese side has lodged multiple representations on different levels and through various channels," foreign ministry spokesman Lu Kang said in a statement on the ministry's website.

China had made representations over the sentences and asked Myanmar to "deal with this case in a lawful, reasonable and justified manner so as to conclude the case properly and return those people to China as soon as possible", he added.

Logging in Myanmar exploded under the former junta -- when China was a close ally -- as the generals tossed aside sustainable forestry practices in a rush to cash in on the country's vast natural resources.

But the quasi-civilian government that replaced outright military rule in 2011 has sought to stem the flood of timber from the country with a ban on the export of raw logs that came into effect in April last year.

At the same time relations with the West have improved markedly, while ties with Beijing have declined.