Terrorists in one of the contested provinces of Syria shot down a Russian fighter jet, the Defense Ministry in Moscow said Saturday.

“[A] Russian fighter jet Su-25 crashed when flying over the Idlib de-escalation zone,” the Defense Ministry told TASS, a state-run media outlet. “According to preliminary information, the jet was brought down with a portable anti-aircraft missile system.”

The missile was fired by Jabhat al-Nusra, the ministry added, which is an affiliate of al Qaeda operating in Syria. Secretary of State Rex Tillerson cited the group’s persistence as evidence that the U.S. needs to retain a presence in the country following the defeat of the Islamic State as a land-holding terrorist organization.

"The pilot was killed while fighting against terrorists,” the Defense Ministry added.

The Russians retaliated with “a series” of airstrikes on the area. “[M]ore than 30 Jabhat al-Nusra militants were killed,” the Defense Ministry also said.

The incident could contribute to the diplomatic sparring that has played out between Russia and the U.S. in recent years. Russian President Vladimir Putin intervened in Syria for the stated purpose of helping Syrian President Bashar Assad defeat terrorists in the country. But U.S. officials noted that Russian airstrikes targeted U.S.-backed rebel groups, instead of the Islamic State, as part of a strategic effort to ensure Assad’s survival. Russian officials countered that they are targeting all terrorists and accused the U.S. side of supporting Jabhat al-Nusra.

"Attempts to make it difficult to finalize the counter-terrorism operation would not be tolerated,” Russian Foreign Minister Sergey Lavrov said in November, while calling for the U.S. to withdraw from Syria.

Tillerson unveiled a plan for a long-term U.S. presence in Syria in December. Tillerson argued that a withdrawal now could allow a resurgence of terrorism in the country, adding that the U.S. would push for a political settlement that sees Assad’s departure from power.

"The nature of the Assad regime, like that of its sponsor Iran, is malignant,” Tillerson said “It has promoted state terror. It has empowered groups that kill American soldiers, such as al Qaeda. It has backed Hezbollah and Hamas. And it has violently suppressed political opposition. Bashar al-Assad’s grand strategy, to the extent he has one beyond his own survival, includes hosting some of the most radical terrorist elements in the region and using them to destabilize his neighbors.”