By the mid-10th century, there was already a Christian community among the Rus' nobility, under the leadership of Bulgarian and Byzantine priests, although paganism remained the dominant religion. Princess Olga of Kiev was the first ruler of Kievan Rus' who became a Christian. Her grandson, Vladimir of Kiev, made Rus' officially a Christian state. The official Christianization of Kievan Rus' is widely believed to have occurred in 988 AD, when Prince Vladimir was baptised himself and ordered his people to be baptised by the priests from the Eastern Roman Empire.