Kurdish forces who have become the main ally of the United States in the fight against Islamic State in Syria on Monday accused Turkish forces of shelling their positions near frontlines in the north of the country.
Turkish forces opened rocket and heavy artillery fire on Kurdish People's Protection Units (YPG) in the villages of Balyunieh and Ain Diqna, the Hawar news agency, which is close to the Kurdish forces, reported.
The Firat news agency, which is also close to the Kurdish forces, reported that a YPG fighter was killed in Turkish shelling on the nearby Kurdish enclave of Efrin on Saturday.
The YPG is the main component of the Democratic Forces of Syria (DFS) alliance, which last week launched an offensive aimed at capturing areas north of Islamic State's de facto Syrian capital of al-Raqqa.
Hawar reported that on Sunday DFS forces opened a new front in that offensive aimed at moving along the eastern bank of the Euphrates river towards the city of al-Tabqa just west of al-Raqqa.
Turkish President Recep Tayyip Erdogan on Saturday denounced US support for the Kurdish-led offensive. Ankara accuses the YPG of being terrorists, pointing to their close links to the banned Kurdistan Workers' Party (PKK) rebel group in Turkey.
Meanwhile, Yeni Safak newspaper reported Monday that Turkey is stepping up security measures on its border with Syria, including plans to install computerized automated firing systems.
The weapons would be part of so-called "smart towers" equipped with thermal imaging systems to prevent illegal border crossings.
If anyone gets within 300 metres of the border a warning will be sounded in three languages, which, if not heeded, will trigger the weapons system, according to the report in the pro-government daily.
The Defence Ministry has not responded to requests for comment on the reports.
Turkey was heavily criticized for its once-porous border with Syria, which allowed fighters to cross over and join rebels in the country's civil war. Some eventually joined Islamic State.
Last year, Turkey began to significantly step up border security, especially in areas bordering territory controlled by Syrian Kurds.