The Pentagon issued a terse warning Friday that the U.S. would act to defend its troops after a close call in Northern Syria in which a pair of Syrian warplanes bombed dangerously close to U.S. special operations forces and the U.S. military scrambled fighter jets.

"We will ensure their safety and the Syrian regime would be well advised not to do things that would place them at risk," said Pentagon spokesman Capt. Jeff Davis.

Asked specifically if that meant the U.S. would shoot down Syrian warplanes that threated U.S. forces, Davis said, "We have the inherent right to self defense. When anybody is striking against U.S. forces, and U.S. forces are at risk, we have the right to take action."

The incident Thursday involved a "small number" of U.S. special operations advisers who are working with Kurdish forces battling the Islamic State in Northern Syria in an area the Pentagon says was "well-known to everybody to include the regime, that the coalition is actively engaged in operations against ISIL."

A pair of Syrian planes, identified by the Pentagon as Russian-made Su-24s, bombed a location where Kurdish fighters were in operation with the American advisers.

There were no casualties reported, but the Pentagon said the Syrians had no business attacking an area where the coalition was fighting the Islamic State.

"We view instances that place coalition personnel at risk with the utmost seriousness," Davis said.

The U.S. quickly scrambled aircraft to confront the Syrian planes, which were departing the area when the coalition planes arrived.

The U.S. also called the Russians on a safety of flight hotline, and they insisted the planes were not Russian aircraft.

The warning to Syrian warplanes was delivered through the Russians, according to the Pentagon.

"We did make clear that U.S. aircraft would defend troops on the ground if threatened," Davis told reporters at the Pentagon.

As a result of the Syrian attack, the U.S. has increased combat air patrols over areas where U.S. troops are located in Syria.

About 300 U.S. special operations forces are advising and assisting counter Islamic State fighters in Syria, according to the Pentagon.