Protesters wear clothes reading Free Olivier during a solidarity demonstration with Belgian aid worker Olivier Vandecasteele in Brussels on December 25, 2022. AFP
The website of Iran's judiciary said a Revolutionary Court sentenced 41-year-old Olivier Vandecasteele to 12.5 years in prison for espionage, 12.5 years for collaboration with hostile governments, and 12.5 years for money laundering.
He was also fined $1 million and sentenced to 2.5 years for currency smuggling.
Under Iranian law, Vandecasteele would be eligible for release after 12.5 years. The judiciary website said the verdicts can be appealed.
Iran has detained a number of foreigners and dual nationals over the years, accusing them of espionage or other state security offenses and sentencing them after secretive trials in which rights groups say they are denied due process.
Critics accuse Iran of using such prisoners as bargaining chips with the West, something Iranian officials deny.
Iran has not released any details about the charges against Vandecasteele. It is unclear if they are related to anti-government protests that have convulsed Iran for months or a long-running shadow war with Israel and the US marked by covert attacks on Iran's disputed nuclear program.
The nationwide protests began after the death in police custody of 22-year-old Mahsa Amini, who was detained for allegedly violating Iran's strict dress code.
Rallying under the slogan "Women, life, freedom,'' the protesters say they are fed up with decades of social and political repression. Iran has blamed the protests on foreign powers, without providing evidence.
Vandecasteele's family said last month that he has been detained in an Iranian prison for months and has been on a hunger strike.
They said he was deprived of access to a lawyer of his choice and is suffering from serious health problems.
Belgium has urged its nationals to leave Iran, warning that they face the risk of arbitrary arrest or an unfair trial. There was no immediate comment on the verdict.
The protests, which have continued for nearly four months with no sign of ending, mark one of the biggest challenges to the Islamic Republic since the 1979 revolution that brought it to power.
At least 520 protesters have been killed and more than 19,300 people have been arrested since the demonstrations began, according to Human Rights Activists in Iran, a group that has been monitoring the unrest.
Iranian authorities have not provided official figures on deaths or arrests.
Iran has executed four people after convicting them of charges linked to the protests, including attacks on security forces. They were also convicted in Revolutionary Courts, which do not allow those on trial to pick their own lawyers or see the evidence against them.
London-based Amnesty International has said such trials bear "no resemblance to a meaningful judicial proceeding."