During World War II, a number of Serbian Orthodox religious sites were damaged or destroyed. During the 1968 and 1981 protests, Serbian Orthodox religious sites were the target of vandalism, that continued during the 1980s. NATO bombing in March–June 1999 resulted in some accidental damages to churches and a mosque. Revenge attacks against Serbian religious sites commenced following the conflict and the return of hundreds of thousands of Kosovo Albanian refugees to their homes. Serbian cultural sites in Kosovo were systematically destroyed in the aftermath of the Kosovo War and 2004 ethnic violence. According to the International Center for Transitional Justice this includes 155 destroyed Serbian Orthodox churches and monasteries as well as Medieval Monuments in Kosovo, which were inscribed on the List of World Heritage in Danger.