Mikhail Lesin, 57, a former press minister accused of curtailing media freedoms in Putin's Russia, also suffered injuries to his neck, torso and upper and lower extremities, the chief medical examiner said.
Putin's spokesman said in response today that the Kremlin expected the United States to provide "detailed official information" about Lesin's murky death on November 5.
The official findings -- made public more than four months after his death -- contradict previous Russian state media reports, citing his family, that said Lesin died of a heart attack.
The New York Times said Lesin's injuries were the result of "some sort of altercation" that took place before he returned to the Dupont Circle Hotel where he was staying.
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Lesin's sudden death triggered a host of conspiracy theories in Russia, but Washington police cautioned it was too early to jump to conclusions and stressed that the medical examiner had concluded that the manner of death was "undetermined."
"We cannot definitively state that foul play was a factor as that would be speculation at this point in the investigation," said police spokesman Dustin Sternbeck, adding that the investigation was ongoing.
Moscow, whose relations with Washington have plummeted over Ukraine and Syria, voiced irritation at the handling of the case.
"We have not received any detailed information through the channels established to deal with these situations," Putin spokesman Dmitry Peskov told reporters in Moscow.
Maria Zakharova, spokeswoman for the Russian foreign ministry, told AFP that Moscow was still waiting for the US State Department to release information related to Lesin's death.