The US-led coalition unleashed airstrikes near the Iraqi city of Mosul targeting top jihadist militants, officials said Saturday, but the fate of the Islamic State group's enigmatic leader remained unclear.

Claims swirled that hardline IS chief Abu Bakr al-Baghdadi had been killed in the attacks late Friday, but US officials could not confirm if he had even been present.

The news came after US President Barack Obama unveiled plans to send up to 1,500 more US troops to Iraq to help battle the militants who have seized a large swathe of territory.

In fresh violence, some 33 people were killed in a wave of car bombings against Shiite areas in the capital Baghdad, highlighting again the security challenge facing Iraqis even within government-controlled zones.

US Central Command confirmed that coalition aircraft conducted a "series of airstrikes" against "a gathering of ISIL leaders near Mosul."

A convoy of 10 armoured vehicles from the group also known as ISIL was destroyed.

"We cannot confirm if ISIL leader Abu Bakr al-Baghdadi was among those present," CENTCOM spokesman Patrick Ryder said in his statement, using another acronym by which the group is known.

- $10 million bounty -

A strike against Baghdadi, who has proclaimed himself the "caliph" of a state straddling Iraq and Syria, would be a major coup for the US-led coalition.

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.

In a video posted online in July, purportedly the first known footage of Baghdadi, he ordered all Muslims to obey him during a Ramadan sermon in Mosul.

Al-Arabiya TV reported Baghdadi had been wounded, while a local Iraqi channel said one of his aides was killed.

Iraqi leaders said the new US military trainers who will aid its fight against jihadists are welcome, but come "late."

Ryder added the US-led strikes were a further sign of "the pressure we continue to place on the ISIL terrorist network."

The aim was to squeeze the group and ensure it had "increasingly limited freedom to manoeuvre, communicate and command."

The new troops will roughly double the number of American soldiers already in the country and marks a deepening US commitment in the open-ended war.

"This step is a little late, but we welcome it," a statement from Iraqi Prime Minister Haidar al-Abadi's office said.

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.

Multiple Iraqi army divisions collapsed in the early days of the jihadist 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, then led by prime minister Nuri al-Maliki, to leave behind a residual US force broke down over the issue of legal immunity.

- Wave of car bombs -

The latest car bombings struck five Shiite-majority areas of Baghdad. They also wounded more than 100 people.

The deadliest single attack was in Sinaa Street in the city's central Karrada district. It killed at least 10.

Two car bombs also hit the Amil area of south Baghdad, and one each exploded in Ameen in the east, Zafraniyah in the centre and Sadr City in the north.

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

In neighbouring Syria, US-led air strikes hit jihadist positions in the north and east, including an oilfield, the Syrian Observatory for Human Rights said.

IS controls most oilfields in Deir Ezzor, which borders Iraq, and smuggled oil is one of the jihadist group's main sources of revenue.