Russia claimed on Wednesday that it was the one who killed Islamic State (ISIS) group spokesman and top strategist Abu Mohamed al-Adnani, but American officials later downplayed that claim and described it as a "joke".
ISIS's news agency Amaq reported on Tuesday that Adnani had been “martyred” in Syria. An American defense official later confirmed that an international coalition air strike had targeted the ISIS spokesman.
On Wednesday, the Russian defense ministry said an Su-34 warplane killed "up to 40" ISIS fighters -- including Adnani -- in a bombing raid near the village of Um Hosh in the province of Aleppo.
"That's a joke," a U.S. defense official told AFP when asked about Moscow's Adnani claim, speaking on condition of anonymity to discuss military operations.
"It would be funny, if not for the character of the campaign the Russians have undertaken in Syria."
Russia has been flying its own bombing campaign in Syria in support of President Bashar Al-Assad since last year, but this is the first time they have claimed to have killed a top-ranking ISIS leader.
The United States says coalition forces had targeted Adnani, who had a $5 million bounty on his head, in an air strike in Aleppo province on Tuesday, but the Pentagon is still assessing the result.
Another U.S. official, again speaking on condition of anonymity, said the strike was carried out by a Predator drone that fired a Hellfire missile at a car in which Adnani was believed to have been traveling.
The Defense Department drone strike was conducted with help from American special operations forces working with the Central Intelligence Agency, the American official said.
The Pentagon is very cautious about confirming the identity of those targeted in strikes, as on previous occasions it has announced deaths only to later learn the individual was still alive.
Pentagon press secretary Peter Cook later said there was nothing to indicate Russia had killed Adnani.
"We don't have any information to support what the Russians have put forward," he was quoted as having told reporters.
Adnani was believed to have been ISIS's second highest ranking leader, after founder Abu Bakr al-Baghdadi.
He was heard from as recently as last May, calling for attacks on the U.S. during the holy month of Ramadan.