Rebels halted on Wednesday a Syrian army push to retake a strategic town on the main highway to Turkey, one day after it was captured by opposition fighters, activists said.
At least 30 rebels and scores of government forces were killed in the fighting near Maarat al-Numaan, 350 km (220 miles) north of Damascus, they said.
"The (Syrian army) column was composed of hundreds of tanks and vehicles. It was stopped at a heavy cost," Abu Musab Taha, a rebel commander in the area told Reuters.
Turkish armed forces have bolstered their presence along the 900-km (560-mile) border and have been responding over the past week to gunfire and shelling coming across from northern Syria, where government forces have been battling rebels who control swathes of territory.
Anas Othman, a resident of Maarat al-Numaan, said the town "is being destroyed" by air strikes and army artillery.
Mohammad Kanaan, an opposition activist from the region, said that 100 fighters and civilians have been killed in Maarat al-Numaan over the last week.
He said security forces had executed 50 army defectors there.
There was no independent verification of the report. Syrian authorities have banned most independent media since the revolt against President Bashar al-Assad started in March last year.
Maarat al-Numaan, a Roman era city famous for a mosaics museum and the grave of Abu Ala al-Maari, an 11th century blind Arab poet, is 75 km south of Aleppo, Syria's business hub.
Opposition sources said the fall of Maarat al-Numaan has further weakened the army supply lines to Aleppo, where urban warfare has been raging for two months.
(Reporting by Khaled Yacoub Oweis, editing by Diana Abdallah)