WASHINGTON - A US fighter plane and a Russian fighter plane flew in the same airspace over Syria on Tuesday, testing new safety protocols designed to avoid air clashes between the two countries.

The Pentagon said that the test lasted about three minutes in south central Syria, which was aimed to "validate the safety protocols established (in) the memorandum of understanding."

"This test was a prudent measure solely to ensure that, in the event coalition aircraft encounter a Russian aircraft during operations in Syria, one of the established and agreed upon modes of communication in the agreement functioned," Pentagon spokesman Jeff Davis said.

The two planes flew within 5 miles (8 km) of each other in the planned communications test, reports cited a military official who spoke on condition of anonymity.

The United States and Russia, both of which are conducting airstrikes against the Islamic State militant group in Syria, last month signed a memorandum of understanding on safe flight operations over Syria, including how to communicate with each other if their jets encounter in the air.

The agreement on air safety in Syria came 10 days after US and Russian aircrafts came within visual range of each other during a mission.

To avoid an inadvertent clash in Syrian airspace during their airstrikes against the IS extremist group, Washington and Moscow started military contacts early October after a long hiatus due to rivalry on the Ukraine crisis.

The memorandum over Syria, however, did not establish any military cooperation between the two countries in Syria; nor did it include intelligence sharing or any sharing of target information in Syria, according to the Pentagon.