A former senior Croatian official has pleaded not guilty to charges that he ordered the abduction, torture and killing of Serb civilians during the nation's war in 1991-95.

Former assistant interior minister Tomislav Mercep also is charged with doing nothing to prevent such crimes while being aware of them as a senior official.

He entered his plea at the start of a trial Friday that is part of Croatia's efforts to meet requirements about dealing with its wartime past as it tries to join the European Union in 2013.

Prosecutors say Mercep personally organized and ordered the illegal imprisonment of some 52 Serb civilians, most of whom were later killed, including a family with a 12-year-old daughter.

The war erupted when Croatia's Serbs rebelled against the country's independence from the former Yugoslavia.