Turkish artillery fire accidentally came close to hitting a U.S. outpost in northern Syria on Friday, CBS News confirms. The Turkish military has been launching artillery and air strikes into Syria but not yet crossed the border in strength.

Three artillery shells landed within a couple of hundred yards from soldiers manning an observation post near the main U.S. base inside Syria, U.S. officials told CBS News.

No one was hurt, but it was exactly the kind of incident Defense Secretary Mark Esper and Joint Chiefs Chairman Mark Milley had warned the Turks about — even to the point of giving them the exact locations of American troops.

"The Turkish military is fully aware, down to explicit grid coordinate details of the location of U.S. forces and we have been in coordination with them," Milley said, "to make sure that they know exactly where American forces are and everyone has been told.

The Turkish Defense Ministry said the artillery fire was not aimed at the Americans but at nearby Kurdish fighters.

"Earlier today, Turkish border outposts south of Suruç came under Dochka and mortar fire from the hills located approximately 1,000 meters southwest of a U.S. observation post. In self-defense, reciprocal fire was opened on the terrorist positions of the attack. Turkey did not open fire at the U.S. observation post in any way. All precautions were taken prior to opening fire in order to prevent any harm to the U.S. base," the ministry said.

Later on Friday, the director of the Defense Department's Press Operations issued a statement opposing Turkey's actions.

"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 U.S. forces are present," Navy Captain Brook DeWalt said. "The U.S. demands that Turkey avoid actions that could result in immediate defensive action."

The longer the fighting goes on, the greater the chances for more accidents. Esper said today he's seen no sign the Turks are heeding his repeated pleas to call off the invasion.