The Turkish army hit Democratic Union Party (PYD) targets around the Syrian town of Azaz using howitzers stationed on the Turkish side of the border, the state-run Anatolia news agency reported.
Turkish forces carried out a similar bombardment Saturday.
Anatolia gave no further details but military sources quoted by Turkish media said the new exchange took place from 0700 GMT.
Turkish forces would continue to strike PYD targets in Syria as long as the army came under fire from their positions, the military sources added.
Turkish media reports said the fire was clearly audible from the border crossing close to the southern Turkish town of Kilis.
NTV television said Turkish forces had also captured three suspected PYD members in Kilis, without giving further details.
In Damascus, the Syrian government strongly condemned the attacks on its territorial integrity and urged the United Nations to act, Syrian state media said.