In this picture taken on Saturday, April 18, 2015, Kurdish boys flash victory signs as they stand on the top of a tank that was destroyed during the battle between the U.S. backed Kurdish forces and ISIS, in Kobani, north Syria.

A U.S. Special Forces raid in eastern Syria killed 32 members of the Islamic State of Iraq and Syria (ISIS) militant group, including three leaders after U.S. officials confirmed on Saturday death of the Islamist organization’s oil chief, a monitoring group said Sunday.

“The U.S. operation killed 32 members of IS, among them four officials, including IS oil chief Abu Sayyaf, the deputy IS defense minister, and an IS communications official,” said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, using another acronym for ISIS.

U.S. officials have said “about a dozen” people were killed in the operation on Friday night, which was conducted by Iraq-based U.S. commandos in order to capture Abu Sayyaf.

Abdel Rahman said three of the four leading officials killed in the raid were from North Africa, but that the ISIS communications official was Syrian.

U.S. President Barack Obama approved the Special Forces operation, a rare use of “boots on the ground” by the United States, which has fought the jihadists almost entirely from the air.

The operation targeted an ISIS compound at al-Omar, one of Syria’s largest oil fields, which is located in the eastern Deir Ezzor province.

A U.S. official speaking on condition of anonymity said the commandos engaged the jihadists “at very close quarters… there was hand-to-hand combat.”

U.S. Secretary of Defense Ash Carter called the operation a “significant blow” to ISIS, while Adam Schiff, a Democrat on the House intelligence committee, said U.S. attacks “have put increasing pressure on the economics undergirding the terrorist organization.”

Syria claims five ISIS leaders killed

Meanwhile, Syrian TV reported on Saturday that the Syrian army has killed five ISIS leaders in an attack in eastern Syria. A headline bar quoting the state TV correspondent in the eastern province of Deir al-Zor identified the five as Saudi, Turkish, Chechen, Jordanian and Iraqi.

ISIS controls wide areas of eastern Syria which it has declared part of a cross-border “caliphate” that includes territory in Iraq.

U.S., allies launch 18 airstrikes

U.S. and allied forces have launched 18 air strikes against ISIS targets in Iraq since Saturday morning, including seven near Ramadi, the western provincial capital recently seized by the militant forces, the U.S. military said.

Other air strikes in Iraq hit near Baiji, Fallujah, Mosul, Sinjar and Tal Afar, the statement said.

U.S. and coalition forces also launched eight air strikes in Syria, including near al-Hasakah and Kobani, the task force said.

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