Iranian authorities blocked human rights lawyer Nasser Zarafshan from boarding a plane to Brussels on March 15 and confiscated his passport, Radio Farda reported.
Zarafshan, who was planning to travel to a forum on environmental issues, told Radio Farda that officials said an "open file in the judiciary" blocked him from traveling as of 10 months ago.
"I do not believe there is a case against me," Zarafshan said. "I am not aware of it. I have been in constant contact with the judiciary lately and they could summon me or even arrest me if they saw the necessity."
Zarafshan, a former political prisoner, has served as an advocate in some of the country's most controversial human rights cases, including the trial of suspects in the murders of Iranian intellectuals in 1998.