MOSCOW, June 14 (RIA Novosti, Ivan Korzun) - Russia is celebrating the Feast of All Saints on June 14, with liturgies in Orthodox churches throughout the country commemorating all known and unknown saints.

The feast, also called All Saints' Sunday, is marked on the first Sunday after Pentecost. It became prominent in the ninth century during the reign of Byzantine Emperor Leo VI the Wise (886-911).

His wife Theophano was known for her piety, giving alms to the poor and monasteries, caring for widows and orphans, and consoling the sorrowful.

After her death Leo built a church, and forbidden from dedicating it to his wife, dedicated it to All Saints, so that his wife would be honored as a righteous woman. He also issued a decree on the date of the feast.

After All Saints' Sunday, the Peter and Paul Fast begins in the Orthodox Church, which this year lasts four weeks.

Western Christians mark All Saints' Day, also called All Hallows Day, on November 1.