WASHINGTON — An American fighter jet shot down a Syrian warplane on Sunday after it dropped bombs near local ground forces supported by the United States, the first time the American military has downed a Syrian aircraft since the start of the civil war in 2011, officials said.

The confrontation represents a further escalation between forces supporting President Bashar al-Assad of Syria and the United States, which has been directing the military campaign in Syria and Iraq against the Islamic State.

The American F/A-18 shot down the Syrian government warplane south of the town of Tabqah, on the same day that Iran’s Revolutionary Guards Corps launched several midrange missiles from inside Iran at targets in Syria, hoping to punish Islamic State forces responsible for last week’s terrorist attacks in Tehran.

The Guards Corp said it “targeted the headquarters and meeting place and suicide car assembly line” of “ISIS terrorists” in the province of Deir al-Zour, where Islamic State forces surround an estimated 200,000 people in a government-held section of the provincial capital of the same name.