ANKARA/BEIRUT — Turkey has killed at least 260 Syrian Kurdish fighters and Daesh (the so-called IS) militants in its four-day-old offensive into the Kurdish-dominated Afrin region of northwest Syria, the Turkish military said on Tuesday.

French President Emmanuel Macron voiced disquiet, a few hours after Turkey's foreign minister said it wanted to avoid any clash with US, Russian or Syrian government forces during its offensive but would do whatever necessary for its security.

The air and ground operation has opened a new front in Syria's multi-sided civil war and could threaten US plans to stabilize and rebuild a large area of northeast Syria — beyond President Bashar Al-Assad's control — where Washington helped a force dominated by the YPG to drive out Daesh militants.

The United States and Russia both have military forces in Syria backing opposing sides and have called for restraint on the part of Ankara's "Operation Olive Branch" to crush the YPG in the Afrin region near Turkey's southern border.

A senior Trump administration official, who briefed reporters on condition of anonymity, said Ankara had sent "conflicting signals" about the scope of the offensive.

"We would urge them to limit the incursion as much as possible," the official said, who said the phone call would happen soon. Another official - as well as Turkey's foreign minister - said Erdogan and Trump planned to speak on Wednesday.

A statement by Macron's office said: "Taking into account Turkey's security imperatives, the president expressed to his Turkish counterpart his concerns following the military intervention launched on Saturday in Afrin."

Erdogan told Macron on Tuesday Turkey was taking all measures to prevent civilian casualties in the Afrin operation, sources at the presidential palace said. The two leaders agreed to stay in close contact on the issue.

The Kremlin said President Vladimir Putin had also discussed Turkey's military operation Erdogan by phone and that Syria's territorial integrity and sovereignty had to be respected.

A Kremlin statement said both men stressed the importance of continuing their two countries' joint work to try to find a peaceful resolution to Syria's crisis. Russia has been Assad's most powerful ally against rebels and militants in Syria.

Turkish Foreign Minister Mevlut Cavusoglu reiterated Ankara's demand that Washington stop supporting the YPG.

Ankara has said the operation will be swift, but Erdogan's spokesman signalled an open-ended cross-border campaign, saying it would end only when some 3.5 million Syrian refugees now living in Turkey could safely return home.

The United States hopes to use the YPG's control in northern Syria to give it the diplomatic muscle it needs to revive U.N.-led talks in Geneva on a deal that would end Syria’s civil war.

Ankara has been infuriated by the US support for the YPG, which is one of several issues that have brought ties between Washington and its Muslim NATO ally close to breaking point.

"The future of our relations depends on the step the United States will take next," Cavusoglu said.

Turkey's military, the second largest in NATO, has conducted air strikes and artillery barrages against targets in Afrin, and its soldiers and allied Syrian rebels tried to thrust into the Kurdish-held district from west, north and eastern flanks.

With heavy cloud cover hindering air support in the last 24 hours, advances have been limited and Kurdish militia have retaken some territory. Turkish troops and the Syrian fighters have been trying to take the summit of Bursaya Hill, overlooking the eastern approach to Afrin town.

The Syrian Observatory for Human Rights, a Britain-based war monitor, said 23 civilians had been killed in Turkish shelling and air strikes, and thousands were fleeing the fighting.

However, Syrian government forces were preventing people from crossing government-held checkpoints to reach the Kurdish-held districts of nearby Aleppo city, it said. — Reuters