Syrian military forces have captured 100 sq miles from Islamic State militants in Aleppo province as it expands operations against the extremist group.
Government forces are moving toward al-Bab, risking a showdown with Turkish troops and allied Syrian forces who have been trying to capture the IS-held town for weeks.
The Turkish-backed forces have also clashed with US-backed Kurdish fighters, who are leading the battle to retake the nearby city of Raqqa, the extremists' de facto capital.
The Syrian government, which is backed by Russia and Iran, has vowed to reassert its control over the entire country.
The military announced the advance on Thursday. It has been seeking to advance in northern Syria since driving rebels out of the city of Aleppo in December.