President Tayyip Erdogan said a decision to jail philanthropist Osman Kavala for life over anti-government protests in 2013 showed that Turkey's courts were independent.
Erdogan said the European Court of Human Rights (ECHR) - which had called for an end to Kavala's detention without a conviction - as well as Ankara's Western allies would have to abide by the court's verdict.
After being detained without a conviction for 4-and-1/2 years, he was convicted and sentenced to life in prison without parole on Monday for allegedly organising and financing nationwide protests in 2013.
Seven others were handed sentences of 18 years. All denied the charges. They say the protests erupted spontaneously and were protected by constitutional rights, denying that they organised them.
Ankara's Western allies, rights groups and the ECHR say Monday's decision was politically motivated and meant to intimidate Erdogan's opponents. Opposition parties also criticised the verdict.
Critics say Turkish courts are under the influence of Erdogan and his AK Party, claims they deny.
Erdogan dismissed this again on Wednesday.
"Our judiciary has proved their independence by not bowing down to blackmail by those outside Turkey and their spokespeople," he said.
He also targeted Kavala personally, comparing him to billionaire George Soros and saying that he was the "behind-the-scenes coordinator" of the protests.
"The decision regarding one person made some circles uncomfortable. This man was the Soros of Turkey and the behind-the-scenes coordinator of the Gezi events," he said.
Rights groups say the case was aimed at criminalising the so-called Gezi protests and creating the perception they were funded by foreign powers.
Turkey now faces suspension from the Council of Europe rights watchdog.
Ankara's Western allies have repeatedly called for Kavala's release, which prompted threats from Erdogan to expel 10 ambassadors last year.
(Reporting by Ali Kucukgocmen and Ezgi Erkoyun; Editing by Jonathan Spicer)
