BAGHDAD (AFP) - Iraq was on Sunday investigating whether the leader of the Islamic State in Iraq and Syria (ISIS), Abu Bakr al-Baghdadi, was killed in air strikes by US-led coalition warplanes targeting the group's leaders.

The death of the elusive Baghdadi would be a major victory for the coalition of countries carrying out air strikes against ISIS and aiding Iraqi forces fighting to regain large areas of Iraq that the extremists have overrun.

The announcement of the strikes came after President Barack Obama unveiled plans to send up to 1,500 more US troops to Iraq to advise and train the country's forces, deepening Washington's commitment to the open-ended war against ISIS.

"Until now, there is no accurate information available," a senior Iraqi intelligence official said when asked about whether Baghdadi had been killed.

"The information is from unofficial sources and was not confirmed until now, and we are working on that," the official said without specifying what the initial reports indicated.

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 (ISIS) leaders near Mosul".

"We cannot confirm if (ISIS) leader Abu Bakr al-Baghdadi was among those present," said Centcom spokesman Patrick Ryder.

The US-led strikes late 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 US$10 million (S$12.5 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 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.

Multiple Iraqi army divisions collapsed in the early days of ISIS northern offensive, leaving major units that need to be reconstituted.

Obama had resisted keeping US troops in Iraq earlier in his term, vowing to end the American presence that began with the 2003 invasion and lasted until 2011.

Talks with the Iraqi government, led by then prime minister Nuri al-Maliki, to leave behind a residual US force broke down over the issue of legal immunity.

With Friday's announcement, Obama will be deploying a force to Iraq along the lines of that considered in 2011, under legal protections similar to those it rejected as insufficient three years ago.

The fight to regain ground from ISIS will take a heavy toll on the predominantly Sunni areas in Iraq that the group now holds.

In Jurf al-Sakhr, an area south of Baghdad that has been retaken from the militants, the conflict left houses burned, buildings and roads rigged with bombs and dozens upon dozens of once-soaring palm trees felled.

Highlighting the enormous security challenges Iraq faces, a wave of car bombs struck Shi'ite-majority areas of Baghdad on Saturday, killing at least 37 people.

Baghdad is hit by near-daily bombings and shootings, some of which have been claimed by ISIS, which, like other Sunni extremist groups, considers Shi'ites heretics.