Ankara: Turkish tanks shelled a Kurdish-held village in northern Syria overnight, wounding at least four fighters, Kurdish forces and a monitoring group said on Monday.
The shelling comes after Turkey carried out air strikes against the Islamic State group in Syria, but also hit Kurdish forces it considers "terrorists" in northern Iraq.
In a statement, the Kurdish People`s Protection Units (YPG) said Turkish tanks hit its own positions and those of allied Arab rebels in the village of Zur Maghar in Aleppo province.
The "heavy tank fire" wounded four members of the allied rebel force and several villagers, the YPG said.
It said there was a second, later round of shelling against Zur Maghar and another village in the same area.
"Instead of targeting IS terrorist occupied positions, Turkish forces attack our defenders` positions," the statement said.
"We urge (the) Turkish leadership to halt this aggression and to follow international guidelines. We are telling the Turkish army to stop shooting at our fighters and their positions."
The Turkish fire was also reported by activists and the Syrian Observatory for Human Rights.
"A number of shells fired by Turkish tanks fell on the village of Zur Maghar, which is controlled by the Kurdish People`s Protection Units," the Observatory said.
Zur Maghar lies on the border with Turkey, east of the town of Jarabulus, which is held by IS.
Observatory director Rami Abdel Rahman said the incident appeared to be the most serious Turkish targeting of Kurdish-controlled areas in the Syrian conflict.
Activists said there had been cross-border fire before but that the overnight shelling was particularly serious because of the context.
In recent days, Turkey has begun striking IS in Syria and arresting the group`s sympathisers at home, but it has also targeted the Kurdistan Worker`s Party (PKK), a Kurdish group with strong links to the YPG in Syria.
Turkey considers the PKK a "terrorist organisation," and in recent days has hit the group`s positions in northern Iraq with the heaviest air strikes since August 2011.
"This shelling comes after Turkey declared war on Daesh (IS) and a war against the PKK," Syrian Kurdish activist Mustafa Ebdi said.
"Now the YPG is facing attacks from IS and Turkey."
The YPG has proved Syria`s most effective force against IS, but its successes have been eyed with suspicion by Turkey because of its links to the PKK.