"We are categorically against this and we condemn the practice of these kinds of arrests of Russian citizens," Kremlin spokesman Dmitry Peskov said, adding that Moscow will do "everything possible" to defend them.

Moscow on Thursday confirmed that Artyom Uss, whose father is the governor of the Siberian region of Krasnoyarsk, was arrested at Milan's Malpensa Airport this week on a US request.

"Our diplomatic missions will naturally take part in protecting the interests of this Russian citizen," Peskov said.

The US Justice Department on Wednesday announced charges against a dozen individuals -- including five Russians -- for "unlawful schemes to export powerful" US military technology to Russia.

It said some of these had "been discovered on the battlefields in Ukraine."

Another Russian citizen was also arrested on a US request on October 17 in Germany.