Sting has cancelled a concert in Kazakhstan's capital Astana over claims of human rights violations on oil workers in the Central Asian country.
In a statement on his website, the singer axed Monday's planned show after Amnesty International told him of "the repression and crackdown" against them.
The singer said the treatment was "unacceptable".
Several thousand oil workers went on strike on 26 May over claims their salaries have been cut.
Police detained strikers for taking part in an unsanctioned protest, and a spokesman for oil company UzenMunaiGas said some 250 employees had been dismissed for breaching their contract terms.
"Amnesty International feel [Sting's] presence in Astana will be interpreted as an endorsement of the presidents' administration and surely will go against everything he has stood for, while supporting Amnesty and the fight for human rights," the statement said.
Sting added: "Hunger strikes, imprisoned workers and tens of thousands on strike represents a virtual picket line which I have no intention of crossing.
"The Kazakh gas and oil workers and their families need our support and the spotlight of the international media on their situation in the hope of bringing about positive change."
Sting had been due to perform as part of city day celebrations as part of his Symphonicity world tour.
Kazakh organisers had initially said the concert had been cancelled for "organisational and technical reasons".
The singer was criticised in 2009 after performing a concert in Uzbekistan, widely regarded as one of the most repressive regimes to emerge from the former Soviet Union.