U.S. fighters scrambled Friday against Syrian aircraft that dropped bombs near American special operations forces on the ground in the northeast in an incident that was the closest the U.S. has come to combat in the wartorn country.

Syrian air force Su-24s made by Russia departed the areas over the contested city of Hasakah before the U.S. warplanes arrived but Pentagon officials made clear that the Syrians would risk attack if they returned.

U.S. and coalition troops were on the ground near the bombing in their train, advise and assist role, according to Navy Capt. Jeff Davis, a Pentagon spokesman.

"The Syrian regime would be well advised not to do things that would place them at risk," he said. "We do have the right of self-defense."

No U.S. or coalition troops were injured in the bombings, which were close enough to pose a threat, he said.

Davis said he could not confirm that the incident in the skies over Hasakah was the closest the U.S. has come to combat in Syria but added that "I’d be hard-pressed to think of another situation like it."

President Barack Obama has barred combat for U.S. ground forces in Iraq and Syria but the ban stops at self-defense.

Davis said that two Syrian Su-24s conducted bombing runs over Hasakah, where there have been clashes in recent days between Syrian regime forces and Kurdish militias backed by the U.S.

American officials immediately contacted the Russians through communications channels set up by the two militaries under a memorandum of understanding, Davis said. "The Russians said it was not them," he said.

The U.S. then scrambled fighters but Davis said the action was not an "intercept" since the Syrian aircraft were leaving the scene.

-- Richard Sisk can be reached at Richard.Sisk@Military.com.