US special forces have killed senior Islamic State leader Abu Sayyaf and captured his wife in a daring night raid in eastern Syria, the White House says.

In the course of the dramatic operation, a Yazidi woman believed to have been enslaved by the couple was rescued as well, officials said.

The raid, with elite American commandos striking at the inner circle of the IS group in their eastern Syrian stronghold, was a rare use of boots on the ground by the US, which has fought the jihadists almost entirely from the air.

On orders from president Barack Obama, the special operations forces based in Iraq sought to capture Sayyaf, who oversaw oil smuggling and military operations for the jihadists.

But the extremist was killed after firing on the US troops, the White House said.

"During the course of the operation, Abu Sayyaf was killed when he engaged US forces," a spokeswoman for the White House national security council, Bernadette Meehan, said in a statement.

His wife, Umm Sayyaf, suspected of being a member of the IS group, was captured, Ms Meehan said.

Sayyaf was Tunisian and Washington informed the Tunisian government of the operation after it was carried out, a US official said.

"The operation also led to the freeing of a young Yazidi woman who appears to have been held as a slave by the couple. We intend to reunite her with her family as soon as feasible," she said.

The Yazidis, a religious minority in north-west Iraq with ancient origins, have been persecuted by the IS jihadists and rights groups say Yazidi women have been kidnapped, raped and sold among the extremists.

Sayyaf's wife was under "US military detention in Iraq" but American officials had not yet decided on her ultimate legal fate.

US officials suspect she "played an important role in IS's terrorist activities, and may have been complicit in the enslavement of the young woman rescued," the White House said.

The American forces went after Sayyaf in Al-Omar in eastern Syria, one of the country's biggest oil fields.

Oil smuggling provides "a key source of revenue that enables [Islamic State] to carry out their brutal tactics and oppress thousands of innocent civilians". the White House said.

Syria not warned of the raid in advance

The raid was carried out with the full approval of the Iraqi government, officials said.

But the White House said the US did not inform Syrian president Bashar al-Assad's government in advance of the raid nor coordinate with Damascus.

"We have warned the Assad regime not to interfere with our ongoing efforts against IS inside of Syria," Ms Meehan said.

"The Assad regime is not and cannot be a partner in the fight against IS."

Shortly before the announcement Syrian state television said the Syrian army killed an Islamic State leader responsible for oil-related affairs, identifying him as Abu al-Taym al-Saudi.

A Syrian military source would not confirm if this was another man or Abu Sayyaf.

US forces suffered no casualties in the night raid, officials said, without offering details about how many troops were involved or what units were deployed.

US commandoes staged a raid in Syria last year to rescue an American journalist held hostage by the IS, James Foley. But the operation failed, and Foley and other hostages had been moved by the time the US forces arrived.

Meanwhile, the Combined Joint Task Force carrying out operations against Islamic State said the US and its allies had conducted six air strikes in Syria and 15 in Iraq since early on Friday.

In Syria, air strikes using bomber and fighter aircraft hit near Al Hasakah while in Iraq, air strikes hit near Al Hawijah, Bayji, Mosul, Ramadi, Sinjar and Tal Afar, it said.

AFP/Reuters