BEIRUT (AP) — Opposition activists say U.S.-backed Syrian rebels have shot down a government warplane in the southeast, with the fate of the pilot still unknown.

The downing of the plane on Monday came after days of clashes between government forces and U.S.-backed rebels in eastern Syria.

The Britain-based Syrian Observatory for Human Rights said the warplane was shot down by the "Eastern Lions" rebel group and crashed in an area called Tel Dakweh.

Mozahem al-Salloum, of the activist-run Hammurabi Justice News network, said the warplane was a Russian-made MiG and that a search is underway for the pilot.