The Turkish secret service has killed a leader of the banned Kurdistan Workers' Party (PKK) in Syria, the state news agency said Monday.
"The MIT neutralised Yasar Cekik, one of the leaders of the PKK/YPG, who was on the red list for those wanted for terrorism in the Tal Rifaat region," some 20 kilometres (12 miles) inside Syria, the Anadolu agency said.
Ankara said Cekik was an important local leader of the Syrian Kurdish People's Defence Units (YPG), which it sees as an offshoot of the PKK, which has led a decades-long insurgency against Turkey.
It maintains he was the mastermind behind several attacks on Turkish security forces within Turkey.
Syrian rebel groups supported by Turkey took the town of Tal Rifaat from Kurdish forces Sunday, according to the UK-based Syrian Observatory for Human Rights, as part of a lightning rebel offensive that took control of the country's second city Aleppo, in a major reverse for President Bashar al-Assad.
Tal Rifaat is located next to a strip of land long occupied by Turkey in northern Syria from which it has launched operations against the Kurds.
The Observatory warned that around 200,000 Syrian Kurds in north Aleppo province have been "besieged by pro-Turkey factions".
Turkish forces and their proxies have controlled swathes of territory in northern Syria since Ankara in 2016 began successive ground operations to expel Kurdish fighters it links with terror attacks on Turkish soil.
Abbas Araghchi, the Foreign Minister of Iran, one of Bashar's top backers, is meeting his Turkish counterpart Hakan Fidan and President Recep Tayyip Erdogan in Ankara Monday, with Turkey saying it would support moves "to reduce tension".