"There was less than an hour of notification time before the strikes were conducted, that's not enough time," coalition spokesman US Colonel John Dorrian said.

"This was notification, certainly not coordination, as you would expect from a partner and an ally in the fight against ISIS."

Dorrian's remarks came as the Syrian Observatory for Human Rights monitoring group said the toll in the Turkish air raids in northeastern Syria had risen to 28. Another 19 were wounded.

He said US forces were operating within six miles (10 kilometers) of strikes in northern Iraq where a "significant number" of Peshmerga fighters were killed.

Dorrian said there had been "diplomatic activity" between the US and Turkey following the strikes.

"We let the Turks know that the amount of time that was being provided for the strikes was inadequate for us to ensure safety of our forces on the ground," he said.

The US State Department said Tuesday it was "deeply concerned" that the strikes were conducted "without proper coordination either with the United States or the broader global coalition" that is fighting IS in Syria and neighboring Iraq.

Turkey, which backs Syrian rebel groups and which launched a ground operation in northern Syria last year, vowed to continue acting against groups it links to the outlawed Kurdistan Workers' Party, or PKK.

The strikes have underlined the complexities of the battlefields in Iraq and Syria, where twin US-backed offensives are seeking to dislodge IS from its last major urban strongholds.

They could also exacerbate tensions between Ankara and its NATO ally Washington, which sees the Kurds as instrumental in the fight against IS.