Washington, Sep 23 (PTI): The US and its allies have expanded their war against the Islamic State by launching aggressive airstrikes against an array of targets of the militant group in Syria, the Pentagon has said.

"I can confirm that US 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," Pentagon Press Secretary Rear Admiral John Kirby said yesterday.

However, he did not give details of the airstrikes arguing that operations are still ongoing.

"The decision to conduct theses strikes was made earlier today (Monday) by the US Central Command commander under authorization granted him by the commander in chief," Kirby said.

President Obama and other US leaders had recently said that they would order airstrikes against Islamic State, also known as ISIL, -- which the CIA estimates has up to 31,000 fighters at its disposal —- strongholds in Syria.

The IS controls much of eastern Syria and has used its bases there as a springboard for seizing territory in neighboring Iraq.

On August 8, Obama launched airstrikes in Iraq against IS and since then has been building support for a coalition.

The IS stunned the international community in June when it swept through regions of northern Iraq, capturing the major cities of Mosul and Tikrit and halting less than 50 kilometres from Baghdad.