WARSAW (Reuters) -Poland’s largest refiner PKN Orlen said it was continuing to buy Russian crude oil to ensure the security of supplies, as some European buyers shunned Russian barrels over Moscow’s invasion of Ukraine. The conflict has pushed the United States and some Western oil firms to stop buying Russian oil amid talk of potential supply from Iran, Venezuela and the United Arab Emirates. “For the Orlen Group, the priority is to ensure the continuity of operation of our European refineries and the energy security of Poland and the entire region, including Lithuania, Latvia, Estonia, the C…