President Bashar al-Assad's fighters have seized three villages since yesterday, bringing them to around four miles from Al-Bab to its southwest, the Syrian Observatory for Human Rights said.
Turkish forces, meanwhile, have gathered to the north of the town, the Britain-based monitor said.
Al-Bab has come under heavy assault in recent weeks, with Turkish, Russian and Syrian warplanes carrying out strikes in or around the town.
Yesterday, the Britain-based monitor said 10 civilians including a child were killed in Turkish air strikes and shelling in the area.
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Several this month have been joint operations with Russia.
Turkish officials say the utmost is done to avoid causing civilian casualties, and have denied claims that civilians have been killed in previous raids.
Turkey's state-run Anadolu news agency reported yesterday that the latest round of raids had killed 22 IS "terrorists".
IS is not included in a fragile nationwide ceasefire in force since December 30 that led to peace talks jointly organised by Turkey, Russia and Iran in Kazakhstan this week.
Moscow and Tehran have supported the government.
The Observatory, which relies on a wide network of sources inside Syria for its information, says it determines whose planes carry out raids according to type, location, flight patterns and munitions used.