The Pentagon is casting doubt on Russia's claim that an airstrike from one of its bombers killed Abu Mohammed al-Adnani, a senior Islamic State leader who the terrorist group reported was killed Tuesday near Aleppo.

Pentagon spokesman Peter Cook said Wednesday that Adnani has been tracked by the U.S. and targeted in a precision strike near al Bab, which is northeast of Aleppo.

"We have no information to support Russia's claim that it carried out a strike against Adnani," Cook said, noting that while the U.S. has made targeting Islamic State leadership a key aspect of its bombing campaign, Russia has not conducted this kind of precision strike in the past.

"I would just note that from the start, Russia, as you know, has spent most of its time, its military campaign supporting and propping up the Assad regime," Cook said. "It has not devoted much, if any, effort that we're aware of targeting ISIL's leadership. And at the same time, we have not seen the Russian military campaign use precision weaponry on a regular basis as well."

Cook declined to provide any details that would discount, or to definitively rule out the Russian claim, such as whether any Russian aircraft were in the area at the time, and did not confirm the U.S. has definitely killed the Islamic State leader.

Pressed for an explanation for why Russia would try to take credit for a U.S. airstrike, Cook said that was a question for the Russians to answer, but offered that "maybe it's just a misunderstanding on their part."

Pentagon sources indicated Adnani was traveling in a vehicle when it was struck from the air by a missile fired from a U.S. drone.

A news agency affiliated with the Islamic State posted a statement Tuesday saying Adnani was conducting surveying operations around Aleppo when he was "martyred."

A post on the Russian Defense Ministry's Facebook page claimed a Russian Su-34 carried out a strike against a large concentration of Islamic State militants Maaratat-Um-Haush in Aleppo province and killed up to 40 people, and that Adnani was among the dead.

"I'm scratching my head over why the Russians made this claim," a Pentagon source said. "It's possible they think they did it."

He also said it could take days, weeks, or months to confirm Adnani was killed.

"The United States of America does not rush to Facebook to make claims it can't support. We employ substantial rigor to the confirmation process."

While Cook stopped short of confirming Adnani's death, he nevertheless said it would be a significant loss to the Islamic State

"His elimination would be a significant blow to ISIL, significant blow to ISIL's leadership, and importantly, a significant step in reducing ISIL's ability to conduct external attacks outside of Iraq and Syria," Cook said.