MOSCOW (AP) — Russian warplanes in Syria have flown their first joint combat mission with the Syrian air force, Russia's Defense Ministry said Thursday.

The Defense Ministry said that a pair of Syrian MiG-29 fighter jets escorted two Russian Su-25 ground attack aircraft during Thursday's mission.

The ministry said that Syrian pilots had previously visited the Russian base to discuss details of the mission. It released a video showing the Russian planes taking off from Hemeimeem air base and being joined in flight by the Syrian jets.

Russia has conducted an air campaign in Syria since Sept. 30. Moscow has insisted that Russian warplanes are focusing their strikes on the Islamic State group and other extremists, but the U.S. and its allies say they also hit moderate groups fighting Syrian President Bashar Assad's army.

According to an agreement with Syria signed in August, the text of which was officially released Thursday, the Russian military can use the air base in Hemeimeem free of charge for an indefinite period. Each party can terminate the agreement at a one-year notice.