Local media and the Syrian Observatory for Human Rights said Syrian regime forces took control of the city of Maarat al Numan located in the northwestern province of Idlib.
Syrian regime forces took control of a town south of Idlib city on Tuesday in a significant advance for regime leader Bashar al Assad as he seeks to recapture territory in the country's northwest, a war monitor and state media said.
Assad's campaign to regain Idlib province, the last opposition bastion in a nearly nine-year-long civil war, has sparked a new exodus of thousands of civilians towards the border of Turkey, which backs some opposition groups fighting Assad.
Syrian broadcaster Al Ikhbariya said regime forces entered Maarat al Numan, 33 km (20 miles) south of Idlib city, on Tuesday and were combing its districts while advancing further into the town. The regime's news agency SANA said later the forces had "liberated most of the town's districts."
"Fighting is now going on inside," said Syrian Observatory for Human Rights head Rami Abdul Rahman, adding that regime and Russian warplanes are pounding the area.
The Syrian Observatory for Human Rights said via WhatsApp that regime forces "took full control" of Maarat al Numan, the second largest town in Idlib province, after entering it backed by Russian air strikes.
The push into the town of Maarat al Numan came as Syrian forces were also advancing against militant and opposition positions west of the city of Aleppo, according to regime media and opposition activists.
Maarat al Numan, which has been in opposition and militant hands since 2012, sits on the highway linking Damascus with Aleppo. The main artery is coveted by the regime as it tries to rekindle a moribund economy.
The renewed fighting comes despite a January 12 ceasefire deal between Turkey and Russia, which back opposing sides of the conflict. Turkey already hosts more than 3.5 million Syrian refugees and fears millions more could soon cross the frontier.
Turkey's Defence Ministry on Tuesday warned Turkish forces would retaliate "in the strongest way, without hesitation" against any attack on its observation posts in Idlib province by Assad's forces.