Former Surinamese President Desi Bouterse, whose conviction for involvement in the killing of 15 people more than four decades ago was upheld in December, must report to a jail to serve his sentence, the public prosecutor said on Wednesday.

A three-judge panel affirmed the convictions of Bouterse and four others in the execution of 15 government critics, including lawyers, journalists, union leaders, soldiers and university professors in December 1982.

Bouterse, 78, dominated politics in the former Dutch colony for decades and left office in 2020. He denied the charge but was sentenced to 20 years in prison. The former president and army leader had until Monday to request a pardon but did not do so. He is to appear at a jail in the country alongside four co-defendants on Friday, the public prosecutor added.

It was not immediately possible to contact Bouterse or his lawyer.Current President Chan Santokhi investigated the so-called “December murders” as a police commissioner and later, as justice minister, pushed for the case to move ahead.

The court ruled in 2019 that Bouterse had overseen an operation in which soldiers abducted 16 leading government critics, murdering 15 of them at a colonial fortress in the capital Paramaribo. One trade union leader survived and testified against Bouterse, who seized power in a 1980 coup against Suriname’s first prime minister just five years after independence.

Bouterse has said in the past the murdered men were connected to an invasion plot involving the Netherlands and the United States. He led the country through the 1980s as head of a military government, then assumed office again in 2010, securing re-election five years later.

Hugo Essed, the lawyer representing the victims’ families, told a local radio station he feared unrest following the order and called on security forces to be alert. While Bouterse’s party has consistently tried to halt the case, which began in 2007, it urged calm after the December ruling.