River buses sail past on the Moskva river, near the Kremlin (background) in Moscow on May 12, 2018. (AFP PHOTO)

Russia has officially declared a former Kremlin official alleged to have been a CIA informant missing and is looking for him, according to an entry in the Interior Ministry's database, the RIA news agency reported on Monday.

US media reports, confirmed to Reuters by two sources, have said a CIA informant in the Russian government was extracted and brought to the US in 2017.

The official may have been a man called Oleg Smolenkov, who disappeared with his wife, Antonina, and three children while on holiday in Montenegro in June 2017, Russian daily newspaper Kommersant has reported.

RIA said the interior ministry's database showed that Smolenkov had now been declared missing and that the ministry was looking for him.

US media reports have described the informant as a high-level CIA source.

The Kremlin has confirmed that Smolenkov worked in the Russian presidential administration, but said he was fired in 2016-17 and was not senior.

Russia asked the US via Interpol earlier this month to clarify the whereabouts of Smolenkov after Russian news reports identified a house listed as belonging to a man with his name in Stafford, Virginia, near Washington DC.

The area where the house is located is inhabited by many former US military and FBI personnel, according to RIA.

Russia fired officials who allowed Smolenkov to flee the country via Montenegro, which he did in contravention of a ban on employees of the presidential administration traveling to the Balkan country, Interfax news agency reported on September 13.