Updated

Hundreds of Poles have prayed for victims of World War II-era massacres by Ukrainians on an anniversary that remains a sore point between the neighbors.

Tens of thousands of ethnic Poles, including men, women and children, were killed during 1943 and 1944 in what was then Nazi-occupied Poland and is now western Ukraine. Poles are marking the July 11, 1943 anniversary of the worst bloodshed of the period, in which Nazi-affiliated Ukrainian nationalists attacked 100 villages.

Under communism, talk about the killings was taboo and historians are only now revealing the details.

Families who once lived in the area prayed Sunday at Poland's Jasna Gora shrine.

Poland wants to call the killings genocide, but Ukraine is opposed. Ukraine's president declined attendance at a remembrance ceremony in Ukraine.