BELGRADE, Serbia-A leading Serbian human rights group said Tuesday it has filed a criminal complaint against former commanders and members of special police units for alleged atrocities in Kosovo.

The Humanitarian Law Center alleged in a statement that the special units took part in "numerous massive war crimes" against ethnic Albanian civilians in Kosovo during the 1998-99 conflict.

The group said that those responsible for the crimes have not been punished and still hold important positions within the Serbian police.

The War Crimes Prosecutor's Office, which decides whether to launch formal proceedings, confirmed it has received the complaint and said it will study it.

Serbia has tried several former security officers in connection with Kosovo atrocities but the Humanitarian Law Center said more must be held responsible.

The group said several ethnic Albanian civilians were killed by the special police in 1998-99, including an elderly couple and a mentally disabled 30-year-old. It said the accounts were based on testimonies from policemen who refused to take part in the killings.

Thousands of people were killed in Kosovo before NATO bombing in 1999 forced Serbia to pull out its troops.