A US special forces raid in eastern Syria killed 32 members of the Islamic State jihadist group, including four leaders, a monitoring group said Sunday.
"The US operation killed 32 members of IS, among them four officials, including IS oil chief Abu Sayyaf, the deputy IS defence minister, and an IS communications official," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
US officials have said "about a dozen" people were killed in the operation on Friday night, which was conducted by Iraq-based US 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 IS communications official was Syrian.
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US 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 IS compound at al-Omar, one of Syria's largest oil fields, which is located in the eastern Deir Ezzor province.
A US official speaking on condition of anonymity said the commandos engaged the jihadists "at very close quarters... there was hand-to-hand combat".
US Secretary of Defence Ash Carter called the operation a "significant blow" to IS, while Adam Schiff, a Democrat on the House intelligence committee, said US attacks "have put increasing pressure on the economics undergirding the terrorist organisation".