ISTANBUL—Turkish jets bombed Islamic State targets in Syria under the umbrella of the U.S.-led international coalition for the first time, the country’s government said Saturday, as Turkey expands its fight against the extremist group.

The strikes started Friday evening and come after Turkish and U.S. armed forces completed an agreement on Monday, nailing down the technical aspects for Turkey’s warplanes to participate in joint operations against Islamic State, also known as ISIS, ISIL or Daesh.

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