BEIJING, China (AFP) — China on Tuesday vociferously defended a court’s decision to impose the death penalty on a convicted Canadian drug smuggler, escalating a diplomatic row that experts say has descended into a high-stakes game of “hostage politics”.

China’s foreign ministry blasted Canadian Prime Minister Justin Trudeau’s “irresponsible remarks” after he criticised the death sentence handed to 36-year-old Robert Lloyd Schellenberg.

Beijing and Ottawa have been squabbling since last month, when Canada arrested the chief financial officer of top Chinese telecom company Huawei on a US extradition request related to Iran sanctions violations.

In a move observers see as retaliation, Chinese authorities detained two Canadian citizens — a former diplomat and a business consultant — on suspicion of endangering national security.

Then authorities revisited the little-known case of Schellenberg, who was sentenced to 15 years in prison in November for drug offences.

A month later, an upper court took up his appeal and ordered a hasty retrial in the north eastern city of Dalian after ruling that the punishment was too lenient.

The timing and swiftness of Schellenberg’s sentence, and the inclusion of new evidence presenting him as a key player in a plan to ship 222 kilograms (490 pounds) of methamphetamine to Australia, raised suspicion among observers.

“Playing hostage politics, China rushes the retrial of a Canadian suspect and sentences him to death in a fairly transparent attempt to pressure Canada,” Human Rights Watch executive director Kenneth Roth said in a tweet.

Donald Clarke, a George Washington University professor specialising in Chinese law, coined an even grimmer term for the situation: “death threat diplomacy”.

“The Chinese government is not even trying to pretend that there was a fair trial here,” he said.

Trudeau expressed “extreme concern” that China had “chosen to arbitrarily” apply the death penalty.

But Chinese foreign ministry spokeswoman Hua Chunying denied Beijing had politicised Schellenberg’s case, calling on Canada to “respect China’s judicial sovereignty… and stop making such irresponsible remarks”.

Schellenberg plans to appeal, his lawyer Zhang Dongshuo told AFP.

“But it won’t be so quick, it’ll probably be sometime around the middle of next week,” he said.

Ottawa had issued a new travel advisory urging citizens to “exercise a high degree of caution in China due to the risk of arbitrary enforcement of local laws”.

Beijing issued a similar response hours later, calling on Chinese citizens to “travel cautiously” after a Chinese citizen was “arbitrarily detained on the basis of a request of a third-party country”, an apparent reference to Meng’s arrest.

China executes one or two foreigners every year — nearly all for drug offences, according to John Kamm, director of the US-based Dui Hua Foundation rights group.

Experts said retrials are rare in China, especially ones calling for a harsher sentence, but rights groups note that courts are not independent and can be influenced by the ruling Communist Party.