Beijing on Thursday hit out at long jail sentences handed to more than 150 Chinese nationals for illegal logging in Myanmar, in the latest tremor to shake relations between the neighbours.
The mass sentencing, which has sparked outraged editorials in Chinese state-run media, comes after the loggers were arrested in January during a crackdown on illegal forestry activities in northern Kachin state, which borders China.
For years China has hoovered up Myanmar's once abundant raw materials, spurring popular anger in the former junta-ruled country which is set for a general election later this year.
Beijing has asked its smaller neighbour to "deal with this case in a lawful, reasonable and justified manner... and return those people to China as soon as possible", foreign ministry spokesman Lu Kang said in a statement on the ministry's website.
But the Myanmar government said it would not interfere in the judicial process.
"When our citizens break the law in other countries, (they) face sentence by those country's laws. We cannot use diplomacy to intervene. I think China will understand," government spokesman Ye Htut told AFP.
"What is really needed is to stop illegal logging in the future," he added.
A court official in Kachin state, asking not to be named, told AFP Wednesday that 153 Chinese loggers were jailed for life for illegal logging. Life in Myanmar is equivalent to 20 years according to legal experts.
He said a further two males under 18 were handed 10-year sentences without giving details, while a woman was jailed for 15 years on narcotics charges.
An editorial in China's Global Times slammed the "severity" of the sentences, expressing hope that intervention from Beijing could "reverse" the outcome.
"A few cases of Chinese engaging in illegal business in Myanmar have been scrutinized by public opinion, exaggerated as China's economic 'invasion' of the latter," it said, urging the Myanmar public "to look upon China-Myanmar trade in a positive way".
- Strained ties -
It is the latest spat to sully ties between the two countries.
Beijing was Myanmar's closest ally during the later years of military rule, providing a shield from international opprobrium and a lifeline as a trading partner for a junta that badly mismanaged the economy.
But observers say the scale of interests China accrued during that period -- from dams and mines, to a gas pipeline aimed at developing its southern Yunnan province -- caused friction and prodded Myanmar towards reforms in an effort to balance Beijing's power.
Those reforms, started in 2011, have seen the rollback of most western sanctions and the promise of a foreign investment boom.
A general election on November 8 is being keenly watched as a marker of the extent of Myanmar's liberalisation.
One of the first major acts of President Thein Sein, whose quasi-civilian government replaced outright military rule, was to halt construction of the huge Chinese-backed Myitsone dam in Kachin, where a bloody civil war has raged since 2011.
In 2013, China executed notorious Myanmar drug kingpin Naw Kham for the murder of 13 sailors on the Mekong River in 2011.
He was killed by lethal injection, but the decision to first parade him live on television stoked deep resentment in Myanmar.
Earlier this year, Beijing issued a strong rebuke to its neighbour after a Myanmar plane dropped a bomb in Chinese territory leaving five Chinese citizens dead as fighting between government troops and ethnic Chinese Kokang rebels spilled across the border.
Thein Sein's government 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.
But campaigners say both Myanmar and China have turned a blind eye to enormous smuggling networks on their shared border, transporting everything from weapons and jade to timber and rice.
Logging in Myanmar exploded under the country's former junta as the ruling generals tossed aside sustainable forestry practices in a rush to cash in on the country's vast natural resources.
Vast areas have been stripped bare, partly to feed huge demand across the border in China, with Kachin rebels also accused of building their war chest on the profits from logging and mining.