The Mongols had been proselytised by Christian Nestorians since about the 7th century and many of them were Christians. Many Mongol tribes, such as the Kerait, the Naiman, the Merkit, the Öngüd, and to a large extent the Kara Khitan, were Nestorian Christian. Under Mongka, the main religious influence was that of the Nestorians. Overall, Mongols were highly tolerant of most religions, and typically sponsored several at the same time. Rabban Bar Sauma testified to the importance of Christianity among the Mongols, during his visit in Rome in 1287: