Istanbul: Turkish forces advanced deeper into north-east Syria as part of a campaign to oust Kurdish fighters from the area, Turkey's Defence Ministry said, expanding an offensive that has drawn a sharp rebuke from the international community.

The operation, including air and ground forces, targeted villages along the border with Syria and "continued successfully" on Thursday, the second day of the offensive, the ministry said in a statement.

Smoke billows from targets inside Syria during bombardment by Turkish forces on Thursday. Credit:AP

The Britain-based Syrian Observatory for Human Rights said more than 60,000 people had fled their homes since the first strikes on Wednesday, while the UNHCR estimated it at tens of thousands. Aid agencies warned that nearly half a million people near the border were at risk "if all sides do not exercise maximum restraint and prioritise the protection of civilians."

Residents fled with their belongings loaded into cars, trucks and motorcycle rickshaws, while others escaped on foot.