US special forces killed a senior leader of Islamic State (IS) group in eastern Syria, Secretary of Defense Ashton Carter said on Saturday.The raid was carried out at the direction of US President Barack Obama to conduct an operation in eastern Syria to capture an IS leader known as Abu Sayyaf and his wife Umm Sayyaf, Xinhua quoted Carter as saying in a statement."Abu Sayyaf was killed during the course of the operation when he engaged US forces," said the statement, adding that Umm Sayyaf was captured.Abu Sayyaf was believed by the US military as a senior IS leader involved in overseeing IS's oil and gas operations, a key source of revenue for IS daily operations.No US forces were killed or injured during the operation, the statement said.