Russia's prosecutor general sent a formal request to the US Justice Department on Friday for official information regarding the mysterious death of a former close adviser to Russian President Vladimir Putin in a Washington hotel room.
Recent media reports said former press minister Mikhail Lesin, who once led several of Russia's most popular news outlets and helped create the state's English-language news channel RT, was killed by blunt-force trauma to the head.
Lesin was found dead in Washington's Dupont Circle Hotel in November. Initial reports said he apparently died of a heart attack.
The request for official information "was sent in accordance with the agreement between Russia and the US on joint legal assistance on criminal cases," a spokesman for Prosecutor General Yury Chaika told the Interfax news agency.
Russia's Foreign Ministry said Friday that Washington had not sent Moscow "any substantial information" about the case.
"We are awaiting from Washington the pertinent explanations and official information concerning the investigation," Foreign Ministry spokeswoman Maria Zakharova said in a statement.
Zakharova told dpa that Moscow has had to rely on a statement by a city medical examiner in Washington for information about the case.
The statement surfaced in the media, and Moscow had to verify its authenticity, Zakharova said.
The mysterious circumstances surrounding Lesin's death have sparked swirling speculation.
Critics claim Lesin played a key role in the muzzling of independent media in post-Soviet Russia.
His tough actions in the media sector also "caused strong dissatisfaction among the leaders of large federal channels and media holdings," Russia's respected Vedomosti newspaper reported.
In addition to the head trauma, Lesin had injuries to his neck, torso, arms and legs, according to the city medical examiner.
The New York Times cited an unnamed official as saying that Lesin's injuries were apparently inflicted during an altercation.
The report said surveillance camera video showed the media mogul appearing dishevelled as he returned to his hotel room before his death.