The Turkish military has again fired a volley of shots across the border into Syria in retaliation for a fresh round of shelling by the forces of President Bashar al-Assad.

One day after the Ankara parliament formally approved a measure calling for beefed up military presence at the Syrian border and the launch of cross-border operations, Syrian shells landed in the southern Hatay province on Friday afternoon.

Turkish media reported that the latest incident did not lead to any casualties or injuries.

On Wednesday, Syrian shell fire killed five Turkish civilians (all women and children) in the town of Akcakale, where tanks and anti-aircraft missiles have now been deployed.

In a large rally in Istanbul on Friday, Prime Minister Recep Tayyip Erdogan warned that Turkey and Syria (once close allies) were "not far" from war.

"Those who attempt to test Turkey's deterrence, its decisiveness, its capacity, I say here they are making a fatal mistake," he said.