The United States and partner nations are carrying out the first air strikes against Islamic State targets in Syria, the Pentagon said on Monday (September 22), in ongoing operations that mark the opening of a new, far more complicated front in battle against the militants.

Rear Admiral John Kirby, Pentagon press secretary on his Twitter page said: "US military and partner nation forces have begun striking ISIL targets in Syria using mix of fighters, bombers and Tomahawk missiles."

"I can confirm that U.S. military and partner nation forces are undertaking military action against ISIL terrorists in Syria using a mix of fighter, bomber and Tomahawk Land Attack Missiles," Kirby said in a statement.

"Given that these operations are ongoing, we are not in a position to provide additional details at this time."