The opposition Syrian National Council in exile called for the international community to attack Islamic State positions not only in northern Iraq but also in Syria.
IS fighters were nearing the towns of Marea and Aazaz, both bastions of rebel groups battling Syrian
Hereditary President-for-Life Bashir Pencilneckal-Assad
Terror of Aleppo ...
's regime, after seizing a number of villages in Aleppo province bordering Turkey in just three days.
If the jihadists manage to take the strategic towns, this could deal a severe blow to rebel groups battling both regime forces and the IS.
"There is fierce fighting on Saturday between rebels and the IS around Marea," the Syrian Observatory for Human Rights said in a statement.
Marea is the main base of the coalition Islamic Front, the most important rebel grouping that is fighting both Assad's troops and the jihadists.
"The pressure is now on Marea, militarily," said activist Abu Omar, front man for the Marea "revolutionary council."
"The rebels have sent in many reinforcements and weapons to the area in and around Marea," he told AFP, speaking via the Internet.