US special forces have killed a senior Islamic State leader and captured his wife in eastern Syria, American officials said.

The target was identified as Abu Sayyaf, a Tunisian militant who helped direct the group's oil, gas and financial operations.

His wife, Umm Sayyaf, believed to play an important role within the militant group, is in US military custody in Iraq.

Pentagon chief Ash Carter said no US forces had been killed or injured in the overnight raid, which was conducted by US personnel based out of Iraq.

The soldiers were said to have killed Sayyaf when he engaged with them, along with a dozen fighters.

Unnamed US defence officials have briefed US media that no civilians died, even though women and children were present.

The rare ground operation inside Syria was ordered by President Barack Obama.

According to a US defence official, there was an intense firefight during the operation and hand-to-hand combat.

The raid was conducted in the early hours of Saturday local time by Army Delta commandos, the official said.

The team had flown into eastern Syria from Iraq aboard V-22 Osprey aircraft and Blackhawk helicopters.

White House National Security Council spokeswoman Bernadette Meehan said: "The President authorised this operation upon the unanimous recommendation of his national security team and as soon as we had developed sufficient intelligence and were confident the mission could be carried out successfully."

Mission

The IS leader who was killed was a Tunisian national designated by the terrorist organisation as its "emir of oil and gas", according to the US.

During the mission, the soldiers also rescued a young Yazidi woman who appeared to have been held as a slave by the couple, Ms Meehan added.

IS militants captured hundreds of members of the Yazidi religious minority in northern Iraq during their rampage across the country last summer.

A US-led coalition has been striking IS militants in Syria since last year, but this is only the second time troops have carried out a ground raid.

A previous operation was aimed at rescuing Americans held hostage by the group.

The White House said the US did not inform Syrian President Bashar al Assad's government in advance of the raid, or co-ordinate with Damascus.

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

It was not immediately clear why both Syria and the US would claim a similar operation in the Omar oil field.

Elsewhere in Syria, Islamic State has been edging closer to Palmyra, threatening the ancient city's priceless antiquities.