Moscow has warned Tokyo that an expansion of joint U.S.-Japan naval exercises near Russian territory would force it to take "retaliatory measures," Russian Deputy Foreign Minister Igor Morgulov said Tuesday.

Morgulov told Russia’s RIA Novosti news agency that the ramped-up intensity of joint U.S.-Japan naval exercises in the area has prompted “an increase in tensions.”

"We see such actions by the Japanese side as a threat to the security of our country,” he was quoted as saying.