Polish President Andrzej Duda has said it is necessary to renew permissions for the exhumation and reburial of remains of Poles who died in Ukraine and Ukrainians who perished in Poland during the 20th century.

"During the period of World War II and after we agreed with President Petro Poroshenko not to take steps to reinterpreting additional historical legends without having firm scientific proof," Duda said at a joint press conference with Poroshenko in Kharkiv on Wednesday, as reported by 112.ua TV.

According to Duda, it is necessary to focus on conducting historical research of the period and an important aspect of that is the exhumation of remains.

"Exhumation is a very important element. I have delivered a detailed appeal to Poroshenko so that we can overcome this hurdle that has arisen in Polish-Ukrainian relations. It is necessary to reauthorize exhumations on both sides of the border," the Polish president said.

Duda added that he is saddened by the destruction of memorials.