Sputnik is reporting, below, on a statement from Russian military intelligence; if it's correct of course the question would be how that many fighters made it out of Mosul and into Syria.
Intelligence data showed that up to 5,000 Daesh [Islamic State] terrorists have been moved to Syria’s Raqqa and Deir-ez-Zor from Iraq’s Mosul, Russian Reconciliation Center said in a statement on Sunday.
The Russian Defense Ministry’s reconciliation center cited intelligence data that showed that Daesh terrorist group had moved up to 5,000 fighters to the cities of Raqqa and Deir-ez-Zor from the Iraqi stronghold of Mosul.
At the same time, the reconciliation center reported that Daesh had moved considerable forces from their stronghold of Raqqa after the US-backed offensive of Arab and Kurdish rebels was stalled. More forces and equipment were relocated from the vicinity of Deir-ez-Zor.
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