Russia’s most advanced combat warplane, the Su-57 stealth fighter, appears to have begun trial missions over the war-weary Syrian skies.

On Thursday, unverified video footage posted on social media by Syrian political activists showed a pair of new Su-57s being escorted by more conventional Su-35 fighter jets and four Su-25 strike aircraft.

The single-seat, twin-engine planes were allegedly filmed nearby Russia’s Khmeimim Air Base near the southeastern city of Latakia along the Mediterranean coastline and employ state-of-the-art stealth technology to avoid radar detection. They were developed to challenge the U.S. F-22 Raptor — and have been called the “F-22 killer.”

While the new aircraft made its maiden flight last December, military analysts reacted with surprise to Thursday’s sighting, which neither Russian or Syrian officials have officially confirmed.

News sites supporting Syrian President Bashar Assad, however, were quick to welcome the additional firepower to the seven-year-old conflict, which has devastated the Middle Eastern country.

Earlier this month deputy Russian Defense Minister Yuri Borisov, was quoted as saying, “We are buying Su-57 jets for combat trials. The first stage of state trials has been concluded. … As you might imagine … many test flights must be carried out.”

Voice of America, which is working to verify the footage, added that if the mission was real, “it would mark a significant addition to Moscow’s firepower in a theater of war that now features a dizzying array of competing forces and increased military involvement by outside sponsors.”

Those fighting include Russia and Iran supporting the Syrian dictator; Turkey, which is battling Syrian Kurds and trying to stop them from creating their own autonomous state; and various elements of the U.S. military — which worked with the Kurds to defeat the Islamic State terror group.

In December, Russian President Vladimir Putin declared Moscow’s mission in Syria was over, with officials noting that 38 warplanes were returning to Russia.

But analysts now say Moscow appears stuck in the country in a bid to prop up Mr. Assad as fighting continues to rage in rebel strongholds in the northwestern province of Idlib and in the Damascus suburb of Eastern Ghouta. In recent days, pro-Assad jets have pounded rebel-held positions in Eastern Ghouta, reportedly killing more than 300.

Sign up for Daily Newsletters Manage Newsletters

Copyright © 2020 The Washington Times, LLC. Click here for reprint permission.