US Central Command, which oversees American forces in the Middle East, on Saturday said that coalition aircraft conducted a "series of air strikes" against "a gathering of (Isil) leaders near Mosul".
"We cannot confirm if (Isil) leader Abu Bakr al-Baghdadi was among those present," said Centcom spokesman Patrick Ryder.
The US-led strikes late on Friday were a further sign of "the pressure we continue to place on the Isil terrorist network," he said, using another acronym for the Islamic State group.
The aim was to squeeze the group and ensure it had "increasingly limited freedom to manoeuvre, communicate and command".
"I can't absolutely confirm that Baghdadi has been killed," General Nicholas Houghton, the chief of staff of the British armed forces, told BBC television on Sunday. "Probably it will take some days to have absolute confirmation."
Washington has offered a $10 million reward for his capture, and some analysts say he is increasingly seen as more powerful than al-Qaeda chief Ayman al-Zawahiri.
The Iraqi government responded on Saturday to announcements from the US and other countries that trainers would be sent to the country, saying in a statement that: "This step is a little late, but we welcome it."
The government had requested that members of the international coalition help train and arm its forces, the statement said.
"The coalition agreed on that and four to five Iraqi training camps were selected, and building on that, they have now begun sending the trainers," it said.
The new troops announced by Obama would roughly double the number of American military personnel in the country to roughly 3,100.
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Iraq investigating whether Islamic State leader al-Baghdadi killed in US air strikes