Three nongovernmental organizations are urging Azerbaijan to lift a travel ban against investigative reporter Khadija Ismayilova and allow her to travel to Britain to give evidence in the trial of a journalist who is being sued for defamation by an Azerbaijani lawmaker.

Ismayilova was sentenced in 2015 to 7 ½ years in prison on what human rights groups called trumped-up charges. She was conditionally released in 2016 but is still subject to a travel ban.

In a joint statement on January 15, Index on Censorship, Reporters Without Borders U.K., and Transparency International U.K. said lawyers will be seeking permission for Ismayilova to travel to London, where the case against Romanian journalist Paul Radu is set to start next week.

Daniel Bruce, chief executive of Transparency International UK, said that preventing Ismayilova from giving evidence in Radu’s trial was “a clear attempt to bully and silence those who dare expose the truth.”

Radu is a co-founder and executive director of investigative reporting group OCCRP, the Organized Crime and Corruption Reporting Project.

He is being sued for defamation by Azerbaijani member of parliament Cavansir Feyziyev over two articles about money-laundering out of Azerbaijan.

As OCCRP’s lead reporter in Azerbaijan, Ismayilova is a key witness in the case.

Azerbaijan is “unjustly and unfairly” preventing the reporter from traveling to “punish her and stifle the spread of her reporting,” said Index on Censorship’s Chief Executive Jodie Ginsberg.

Rebecca Vincent, U.K. bureau director for Reporters Without Borders, called the travel ban “one of many examples of the Azerbaijani authorities’ long-standing persecution of Khadija Ismayilova for her courageous investigative reporting.”

Dozens of other journalists and activists are currently “subjected to such measures” in Azerbaijan,” Vincent added.

The three NGOs urged the British government to join their call for Ismayilova to be released from her travel ban and be allowed to provide evidence in “this important libel case” against Radu.