An RC-135 aircraft leaves the runway Aug. 13 at Offutt Air Force Base in Nebraska. (Josh Plueger/U.S. Air Force)

A Russian fighter jet came “within several feet” of an Air Force RC-135 reconnaissance plane over the Baltic Sea and lingered by the side of the U.S. plane for several minutes on Monday, U.S. military officials said.

The incident comes amid increased tensions between Russia and the United States following the shoot-down Sunday of a Syrian fighter jet by a U.S. Navy Super Hornet after the Syrians bombed U.S.-backed fighters in northern Syria. Russia, which is aligned with the Syrian government and is carrying out military operations in Syria alongside it, condemned the incident and said Monday that it would track U.S. aircraft over Syria.

The Russian Su-27 maneuvered its wingtip within a few feet of the larger, slower RC-135 for several minutes, said Meghan Henderson, a spokeswoman for U.S. European Command. The Pentagon considered the incident, known as an “intercept,” unsafe because of the “high rate of closure speed” and the “poor control of the aircraft” that the Russian pilot had, Henderson said. 

The news was first reported by Fox News.

The RC-135 is a modified C-135 plane that carries advance sensors that allow airmen inside to detect and make sense of electronic signals. Its crew typically includes more than 30 people, including electronic warfare officers, intelligence operations and maintenance technicians, according to the Air Force.

The Su-27 is a Russian-made jet that was designed to be competitive with “fourth-generation” aircraft used by the Pentagon, such as the F-16 Fighting Falcon and the F/A-18 Hornet.

The United States and Russia both regularly intercept each other’s aircraft, but they are expected to follow an internationally recognized set of procedures when doing so to avoid accidental collisions. In one example, a Russian jet flew within 20 feet of a U.S. Navy P-8 surveillance plane in May over the Black Sea, southwest of Russia. The Pentagon and Russia both said that interaction was carried out in a safe and professional manner.

The U.S. and Russian militaries have had several altercations off the Russian coast in international airspace and waters in the past few years, although none has spiraled into bloodshed.

In April 2016, the pattern included Russian Su-24s zipping no more than a few hundred feet by the USS Donald Cook, a Navy destroyer, “dangerously close” to the ship, U.S. officials said.

In another intercept in that month, A Russian Su-27 barrel-rolled over another RC-135 and came within 50 feet of the plane. The Pentagon decried the maneuver as unsafe and aggressive.