"Warplanes carried out six raids on Thursday against Al-Bab" in the north of the country, the Britain-based Syrian Observatory for Human Rights said.
"Eleven people were killed, including women and children, and 17 were wounded when fighters (jets) fired rockets into a crowded area near a market in the town," southeast of Aleppo city.
IS has been pulling fighters out of the area, with some of its commanders saying the move was in case of Syrian army bombardment and possible American air strikes.
"Our objective is clear: we will degrade, and ultimately destroy, ISIL through a comprehensive and sustained counter-terrorism strategy," Obama said, using an alternative acronym for the group.
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"I will not hesitate to take action against ISIL in Syria, as well as Iraq."
Elsewhere today, air strikes on rebel-held Douma near Damascus killed 17 people, including four children, Observatory chief Rami Abdel Rahman said.
Douma, north of the capital, has been under siege for more than a year.
And in the central province of Hama, the Observatory said regime forces supported by Iranian officers retook a large part of the Halfaya area from rebels and jihadists of the Al-Qaeda-linked Al-Nusra Front.