China lodged a formal diplomatic protest with Myanmar on Thursday a day after the latter sentenced 153 Chinese nationals to life imprisonment for illegal logging. The protest comes amid the illegal smuggling of timber and jade into China from regions along Myanmar’s porous border with China.

Of the 155 Chinese nationals sentenced by the Myanmar court, two were given a jail term of 10 years, Reuters reported. Lu Kang, a spokesman for China’s foreign ministry, said that the country had taken up the matter with Myanmar several times through various channels since the men were arrested in the beginning of the year, China’s state-run Xinhua News Agency reported.

The Xinhua report added that Lu has asked Myanmar to "consider the actual situation of those loggers and deal with the matter in a lawful, reasonable and sensible way." Beijing also urged the Southeast Asian nation to return the Chinese nationals as soon as possible.

The Chinese nationals were reportedly arrested on Jan. 4 from the conflict-stricken Kachin state in northern Myanmar. The military-backed civilian government in Myanmar has been trying to curb the industry and banned the export of raw timber last year, BBC reported. The report added, citing critics, that illegal loggers often make deals with warlords operating in the areas near the border. 

Over 400 vehicles and 1,600 logs were seized during the raid conducted by Myanmar’s military, police and forestry department that led to the January arrests. Aye Myint Maung, a deputy environment minister, told the Parliament in June, according to Reuters, that 10,000 tons of illegal timber has been seized from the loggers since the beginning of the year.

The Chinese group was allegedly arrested during an operation sanctioned by the Kachin Independent Army, an ethnic rebel group active in the area, BBC reported. However, the rebels have denied that they were involved. 

The relationship between the two Asian countries embittered this year over clashes between Myanmar's military and the ethnic Chinese Myanmar National Democratic Alliance Army, along part of the shared border, Reuters reported.