“The real issue here is to deliver Afrin to its real owners,” Mr. Erdogan said. He said that “we have 3.5 million Syrians in our lands” and that Turkey wanted “to send our Syrian brothers back to their own land as soon as possible.”
Mr. Erdogan’s comments came amid growing international dismay over Turkey’s intervention, and amid reports of Syrian fighters massing to join the fight on both sides.
Members of the Free Syrian Army have been joining to fight alongside Turkish troops. Many of them are refugees from Arab villages and towns in the region.
At the same time, hundreds of Kurdish fighters from the American-backed Syrian Democratic Forces, which has been leading the fight against the Islamic State in Syria, were assembling in towns to the east and south of Afrin, according to The Associated Press.
A shopkeeper in Raqqa, who asked not to be named out of fear for his safety, said by text message that a large number of Arab fighters in the Syrian Democratic Forces were being sent from Raqqa to Manbij to prepare for a Turkish attack. His cousin was among 1,000 fighters gathered in Manbij and commanders were telling them an attack was imminent.
Secretary of State Rex W. Tillerson spoke by telephone with his Turkish and Russian counterparts on Saturday to express concern about the situation, a State Department spokeswoman, Heather Nauert, said in a statement.
“We urge Turkey to exercise restraint and ensure that its military operations remain limited in scope and duration and scrupulous to avoid civilian casualties,” the statement said.
France called for an emergency United Nations Security Council meeting to discuss the developments and also urged Turkey to act with restraint, noting that the humanitarian situation was deteriorating in several regions of Syria.
Turkish officials have repeatedly criticized the United States for its support and arming of the Kurdish People’s Protection Units, known as the Y.P.G., which are spearheading the fight against the Islamic State in Syria. Yet they made clear Sunday they did not want to confront American troops in Syria.
Mr. Yildirim said Turkish forces would seek to destroy any logistics supply routes to Kurdish units, but Deputy Prime Minister Bekir Bozdag said United States officials had assured Turkey there were no American troops in the region.
“It is out of the question to have a direct clash between Turkey and the U.S. in the region,” he said at a news briefing for international reporters Sunday.
By nightfall Turkish troops seemed to have advanced only a few miles into Syria.
Syrian fighters allied with Turkish forces claimed to have seized control of Shankal, a village on the northwestern edge of the Afrin district, but Kurdish fighters rejected the claim.
Casualties were reported from both sides, but numbers varied.
Hanadi Hafsi, a homemaker who lives in Reyhanli, a border district in Turkey, said two Syrians and a Turk died Sunday afternoon from shelling by Kurdish militias. The shells fell on a market, killing three and wounding 32, she said. Turkish officials said that only one Syrian had refugee died and that 37 people were wounded.
Turkey’s Foreign Minister Mevlut Cavusoglu condemned the “indiscriminate rocket fire by #PYD/#YPG terrorists” in a Twitter post. “This attack on innocent people shows the real face of #PYD terrorists.”