The Turkish government on Saturday denied that its Army had launched attacks on US special forces deployed in northeastern Syria, as it was earlier claimed by the Pentagon.
"Attacking US forces is out of the question. There's the necessary coordination between our forces and the Americans," Turkey's Defence Minister, Hulusi Akar, said at a press conference held at the military central command in Sanliurfa, about 50 m from the Turkish-Syrian border.
Pentagon sources told Efe news on Friday night that Turkish artillery fire had landed near the US base near the Syrian border city of Kobane.
Turkey aims to carve out a so-called safe zone that will extend about 32 km into northern Syria, stretching from the Euphrates River to the Iraqi border.
The Turkish Army and allied factions of the Free Syrian Army, armed militias opposed to President Bashar Al Assad, began the incursion into northern Syria on Wednesday in an operation dubbed "Peace Spring".
They are fighting against the YPG, which controls most of the region of northern Syria.
The YPG, officially the People's Protection Units, is the largest Kurdish militia in the region and was Washington's key ally in the fight against the Islamic State terror organization.
Ankara considers YPG a terrorist organization indistinguishable from the Kurdistan Workers' Party (PKK), a Kurdish militant group fighting against the Turkish state in eastern Turkey.
Turkey's Defense Ministry said in a statement that the incident on Friday was "self-defence" as its troops had been targeted by mortars fired by YPG fighters located near a US observation post.
Those mortars allegedly hit Turkish city of Suruc, which is facing Kobane on the other side of the border.
In a statement earlier on Friday, the US Department of Defence said: "US troops in the vicinity of Kobani came under artillery fire from Turkish positions at approximately 9 p.m.
"The United States remains opposed to the Turkish military move into Syria and especially objects to Turkish operations outside the Security Mechanism zone and in areas where the Turks know US forces are present."
On Saturday, there were no reports of bombings around the Kobane area, while the Turkish air strikes concentrated in the Syrian city of Ras al-Ayn, one of the points where the Turkish offensive began.
In that area, there have been constant clashes between Syrian rebel militias and members of the YPG.
The Turkish Army claimed on Saturday to have "neutralized" 415 YPG fighters, which means they have been wounded, killed or captured.
They also claimed to have already seized control on 14 towns around Ras al-Ayn and Tal Abyad.
According to the UN more than 100,000 people have fled their homes since the offensive began on Wednesday. But aid groups have said that as many as 450,000 people could be forced to move.