Syria’s opposition National Coalition on Tuesday welcomed US-led air strikes against the so-called ’Islamic State of Iraq and the Levant’ (ISIL) terrorist group.

Syria's opposition National Coalition on Tuesday welcomed US-led air strikes against the so-called 'Islamic State of Iraq and the Levant' (ISIL) terrorist group, but urged sustained pressure on President Bashar al-Assad's government.

"Tonight, the international community has joined our fight against ISIL in Syria," Coalition president Hadi al-Bahra said.

"We have called for air strikes such as those that commenced tonight with a heavy heart and deep concern... We insist that utmost care is taken to avoid civilian casualties," he added.

The comments came after a US-led coalition assembled to battle the ISIL began air strikes against the terrorist group in eastern and northern Syria on Tuesday morning.

The opposition Coalition has backed strikes against IS, but also urged continued attention to the Assad regime.

"We are calling on all our partners to maintain pressure on the Assad regime," Bahra added.

"This war cannot be won by military means alone," he added.

U.S. defense officials announced that American and Arab warplanes hammered ISIL militants in eastern Syria early Tuesday, opening a new front in the fight against the terrorist group.

The so-called National Coalition was the main supporter of the armed opposition since the Syrian crisis erupted in mid-March 2011, leaving thousands of Syrians killed and millions others displaced.