The retrial of a former Croatian police officer convicted in the 1991 murder of three police officials has opened in Croatia's eastern city of Osijek.

Anton Gudelj pleaded not guilty to charges of killing police chief Josip Reihl-Kir and two Croatian Serbs in July 1991. All three victims were known for their efforts to ease ethnic tensions in the Osijek area during fighting that broke out after Croatia declared independence from the former Yugoslavia.

Gudelj fled abroad, and a Croatian court sentenced him to 20 years in prison in absentia in 1994.

German authorities returned him to Croatia two years later to serve his term, but Croatian officials released him under an amnesty in 1997.

He later went to Australia. Croatia's Constitutional Court reinstated the case against him in 2001, and Australian authorities extradited him earlier this year.

Some information for this report was provided by AFP and AP.