A prominent TV talkshow host in Ukraine declared on Tuesday he was going on hunger strike in protest over a decision by state authorities to strip him of his work permit, a move he described as politically motivated, Reuters reports.

His move comes as Ukraine's commitment to Western-backed reforms comes under scrutiny following political upheaval that has delayed billions of dollars in international loans.

The state employment agency said it had withdrawn the work permit of TV journalist Savik Shuster, a Canadian citizen, because he had not informed them he was being investigated by the tax authorities.

"The authorities have returned to a standard post-Soviet state where they don't want to hear anything critical, anything reasonable," Shuster said on his online channel.

"I declare a hunger strike until my right to work in Ukraine is returned to me," he said.

Born in the Soviet Union, Shuster started working in Ukraine in 2004. He hosts the 'Shuster Live' political television show which asks audience members to rate government policy.

As a foreigner who funds his own programs through donations from viewers, he is seen as a relatively independent voice compared to other media outlets, most of which are owned by Ukrainian oligarchs.

"The circumstances of this case raise a number of concerns and questions," said Dunja Mijatovic, media freedom representative for the Organization for Security and Cooperation in Europe (OSCE), a rights body.

He urged Ukraine to ensure "that the journalist's rights are safeguarded and that Shuster is allowed to continue performing his work in a free and safe manner".

Ukrainian President Petro Poroshenko and the newly appointed prime minister, Volodymyr Groysman, also called for the issue to be resolved urgently.

Groysman took office last week, ending months of turmoil amid growing frustration about a lack of progress made in tackling graft and rebuilding the economy after street protests in 2014 ousted a Moscow-backed president.

Pro-European reformists in Ukraine have expressed concern that the latest political reboot will not eliminate the influence of powerful business interests on policymaking.