The Kurdish-led Syrian Democratic Forces Tuesday urged the United States and Russia to work for deescalation after Turkey launched deadly cross-border raids against its fighters and threatened a ground offensive.

Turkey launched a series of air raids on Saturday and Sunday against Kurdish armed groups in northern Syria and northern Iraq, following last week's deadly bomb attack in Istanbul which Ankara blamed on those groups.

In northern Syria, Ankara said it targeted positions of the Kurdish People's Protection Units (YPG), the main component of the US-backed SDF, which is considered a terrorist group by Ankara.

According to Britain-based war monitor the Syrian Observatory for Human Rights, 37 people were killed, most of them fighters, as well as 16 Syrian soldiers. Local Kurdish authorities reported 11 civilians killed.

Turkey's operation "Sword Claw" came after a deadly bomb attack on November 13 in central Istanbul, blamed by Ankara on the YPG and the banned Kurdistan Workers' Party (PKK), who both denied responsibility.

"Our efforts are focused on deescalation and we will do everything in our power to achieve this through contacts with the parties concerned," said SDF commander-in-chief Mazloum Abdi, whom AFP reached by phone from Beirut.

The Kurds control parts of northern and northeastern Syria, a country fragmented by the civil war that started in 2011.

"We are ready to defend our regions but we call on all parties, including the Russians or the Americans, to respect their commitments" to avoid a new Turkish operation, added Abdi.

The United States must "take a firm position to at least stop the bombing of civilians", he said.

- 'Bargaining chip' -

The SDF, backed by the United States, spearheaded the fight to drive the Islamic State group from its strongholds in Syria in 2019. Hundreds of US troops remain deployed in parts of northern Syria.

Abdi again denied any link with the Istanbul attack and accused Turkey of using it as a "pretext" to attack his forces.

He said that "we were also surprised by the very weak position of the Syrian regime", which only announced the deaths of an undetermined number of its soldiers in the Turkish raids.

Turkish President Recep Tayyip Erdogan, whose country has already deployed troops inside Syria near the border, on Monday threatened to launch a new ground operation against Syrian Kurdish forces.

Russia, an ally of the Syrian regime of Bashar al-Assad, called on Turkey the same day to exercise restraint.

The PKK has waged a bloody insurgency for decades and is designated a terrorist group by Ankara and its Western allies. Ankara also considers the YPG to be a PKK-affiliated terror group.

Between 2016 and 2019, Turkey launched three large-scale operations in northern Syria against Kurdish groups.

Abdi charged that Turkey wants "to occupy the entire border area -- 30 kilometres in depth -- to establish a so-called safe zone, to use later as a bargaining chip to maintain influence in Syria".