President Tayyip Erdogan said on Tuesday that 200,000 Syrians had returned to northern Syrian regions controlled by Turkish forces, after criticism from election rivals over the millions of refugees in Turkey.

More than 3.5 million Syrian refugees who fled conflict in their country are living in Turkey, and some Turks see their presence as an economic burden and a threat to jobs.

Their presence has become an issue in Turkey's June 24 presidential and parliamentary elections, with Erdogan's rivals saying they would take steps to ensure the Syrians could return to their country.

Erdogan said many refugees had already returned to the northern Syrian regions of Afrin and Jarablus, where Turkey has launched military incursions to drive back Kurdish or Islamic State (IS) militants.

"As of now, around 200,000 residents from those areas returned back from Turkey," Erdogan told an election rally in Turkey's northwestern Black Sea province of Zonguldak. "And they continue to return. Why? Because it is their own land, we open the path, they return."

Erdogan opened Turkey's borders to Syrian migrants when conflict erupted in 2011. But Ankara has since reversed its "open door" policy, building a wall along the 911 km (570 mile) frontier.