"We are actively coordinating with all relevant parties in Syria to ensure the safety of our people and facilitate their secure relocation... to our safe areas in the northeast of the country," Mazloum Abdi, head of the Syrian Democratic Forces, said in a statement.

A Syria war monitor said late Sunday that around 200,000 Syrian Kurds were "besieged by pro-Turkey factions" who took over the town of Tal Rifaat and nearby villages.

Communications have been cut in Kurdish-majority areas, the Britain-based Syrian Observatory for Human Rights said, raising fears of possible "massacres" of Kurds.

It came days after jihadists of the Hayat Tahrir al-Sham group and its allies launched a surprise offensive in northwestern Syria, seizing swathes of territory from government forces, including Syria's second city Aleppo.

"The situation in northwest Syria has developed rapidly and suddenly, with our forces facing intense attacks from multiple fronts," Abdi, the SDF commander in chief, said in a statement.

"Following the collapse and withdrawal of the Syrian army and its allies, we intervened to establish a humanitarian corridor between our eastern regions, Aleppo, and the Tal Rifaat area, with the aim of protecting our people from potential massacres.

"However, the attacks of the armed groups backed by the Turkish occupation have disrupted this corridor."

Abdi said despite the offensive, "our forces continue to resist to protect our people residing in the Kurdish neighbourhoods of Aleppo".