Slovenia is reburying some 800 victims from a mass grave containing the remains of thousands of people believed killed in the aftermath of World War II by the communist authorities.

The remains will be laid to rest in a memorial park in Maribor, northeastern Slovenia, alongside other victims of post-WWII summary executions. The victims are believed to be mostly Croats and Slovenes from WWII pro-Nazi groups killed by the victorious communists.

Croatian President Kolinda Grabar Kitarovic laid a wreath as part of commemoration ceremonies Thursday. She says "historic truth must be established because it presents a basis for a better future."

The so-called Huda Jama mass grave was discovered in 2009 in an abandoned mine east of Ljubljana. Experts say it contains the remains of up to 5,000 people.