Saudi Arabia has condemned comments by Russia's human rights envoy as "hostile" and an interference in the kingdom's internal affairs.
Konstantin Dolgov had expressed "grave concern" after two people were killed and twenty wounded in what Dolgov described as clashes in eastern Saudi Arabia last Sunday sparked by the arrest of a Shi'ite cleric.
The Saudi interior minister had said the two were killed by assailants and not security forces.
Eastern Province is home to most of Saudi Arabia's Shi'ite community, who complain of discrimination by Saudi Arabia's Sunni monarchy and have staged protests.
Analysts say the exchange between Russia and Saudi Arabia may be in part a result of their opposing stances on Syria.
Based on reporting by Reuters