The Latest on the Syrian conflict (all times local):

1:30 p.m.

The Islamic State group says it has shot down a Syrian warplane near the historic city of Palmyra.

The extremist group's Aamaq news agency said Saturday that the militants downed the jet near the Jazal oil fields west of the city, which is home to famed 2,000-year-old ruins.

The Britain-based Syrian Observatory for Human Rights said a government jet crashed in the Jazal area. It reported IS militants were attacking government positions 4 kilometers (2.5 miles) from Palmyra, which the government recaptured from the extremists to great fanfare in March. The activist-run Palmyra Coordination Committee said the jet was a MiG-23.

The Observatory said Friday that the IS assault near Palmyra has killed at least 49 pro-government forces.

The Syrian government has not commented on the reports.

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12:30 p.m.

Russia says nearly 18,000 people have fled eastern Aleppo in the last 24 hours in a "constant stream" as Syrian government forces close in on the last pocket of opposition control in the northern city.

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said Saturday that Syrian troops have suspended their offensive to allow for the evacuation of civilians, but the activist-run Syrian Observatory for Human Rights says heavy clashes are still underway.

The Russian military's Center for Reconciliation in Syria says 17,971 civilians, including 7,542 children, have left rebel-controlled Aleppo districts in the last 24 hours.

Backed by Russia and other allies, Syrian President Bashar Assad's forces have driven the rebels from nearly all of eastern Aleppo, which was captured by the opposition in 2012.