A court in Montengro has sentenced an investigative journalist to 18 months in prison, on charges that press freedom advocates have described as bogus and intended as a warning to others in the Balkan country.

The court in Podgorica handed down the sentence to Jovo Martinović on Monday, finding him guilty of drug trafficking and criminal associations, despite overwhelming evidence that his contacts with criminal figures were maintained for journalistic purposes.

Martinović was arrested in October 2015 while undertaking an investigation for a French production company on arms trafficking in the Balkans. He spent 15 months in jail before being released on bail before the trial.

“There was no evidence whatsoever against me and overwhelming evidence in my favour,” Martinović said in a telephone interview. He remains free pending an appeal, but if the sentence is confirmed he will spend another three months in jail, taking into account the time he has already spent behind bars.

Martinović believes the case against him was brought after irritation about a number of investigative stories he worked on, as well as a refusal to cooperate with security services, who he says approached him several times and asked him to inform on foreign journalists and diplomats in Montenegro. “I refused to collaborate and spy for them,” he said.

Montenegro gained independence from Serbia in 2006 and joined Nato in 2017. The country hopes to join the EU by 2025. Although many western countries have courted its leaders due to their pro-western rhetoric, critics say the government has been unable to root out corruption and organised crime links, including among its own ranks.

Reporters Without Borders (RSF) ranked Montenegro 103rd out of 180 countries in its annual press freedom index.

“We condemn this iniquitous verdict and sentence and regret that, during the three years of proceedings against this journalist, the judges took no account of evidence and testimony demonstrating his innocence,” said Pauline Adès-Mével, the head of RSF’s European Union and Balkans desk. She said the sentence was “yet another sign of the decline in respect for media freedom and the rule of law in a country that says it wants to join the European Union”.

Last year, Željko Ivanović, the executive editor of the newspaper Vijesti, said there had been more than 25 attacks on Vijesti journalists or premises in the past decade.

Milka Tadić Mijović, the president of the Centre for Investigative Journalism of Montenegro, for whom Martinović has been a contributor, said the case would be felt by all Montenegrin journalists. “This verdict will affect not only Jovo but other journalists in their work, and further deteriorate the country’s already bad record in terms of freedom of expression and media.”