The dark chapters of Poland and Ukraine's history continue to have a bearing on modern day diplomacy after the Polish government on Saturday refused the head of Ukraine's commemoration commission, Svyatoslav Sheremet, entry into Poland.

According to Poland's ambassador to Ukraine, Jan Pieklo, the decision came in response to a ban imposed by Kyiv earlier this year that outlawed the exhumation of Poles killed in Ukraine during the Second World War.

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"I have been also informed that this is a problem that concerns the restarting of exhumations because Sheremet is the person responsible for this," Pieklo told state news agency PAP. The denial of entry to Sheremet prompted the Ukraine government to summon Pieklo.

However, the precise reason why Sheremet was denied entry remains unknown, given that just a day earlier, on Friday, representatives for the Polish and Ukrainian presidency released a joint statement in which they "reconfirmed their commitment to strengthening the strategic partnership."

The statement continued: "The parties agreed that the ban on the search and exhumation works in Ukraine should be lifted."

Warsaw's decision to deny Sheremet entry could be linked to Polish foreign minister Witold Waszczykowski's resolution earlier this month that Poland would bar Ukrainians with supposed "anti-Polish views."

The killing of around 100,000 Poles, most of whom were reportedly women and children, in Volhynia, Ukraine, during the Second World War carries extra sensitivity, after the Polish government last year passed a resolution declaring their deaths at the hands of the Ukrainian Insurgent Army as "genocide."

Ukraine, however, rejects the label, maintaining that the deaths were part of mutual hostilities.

dm/jm (Reuters, PAP)