Istanbul, Aug 20 (IANS): Thousands of unregistered Syrian migrants have until Tuesday to leave Istanbul or face expulsion from Turkey's biggest city, a media report said.

Authorities have told the migrants to return to the province they were registered in, as part of a bid to relieve pressure on the city, reports the BBC.

But some Syrians told the BBC that many were being deported to Idlib, inside Syria, where fighting is escalating.

They said that many were being forced to sign voluntary return documents that they cannot read or understand.

The order to relocate was issued late last month, giving those affected about a month to comply.

Announcing the move last month, Istanbul Governor Ali Yerlikaya said Syrians with the right to be in the city should carry their passports and identity documents with them at all times, and announced continuous checks at bus and train stations.

Since Syria's civil war began over eight years ago, some 3.6 million Syrians have fled north to neighbouring Turkey.

About half a million are registered in Istanbul - but estimates suggest twice that number are living there, having travelled from the provinces they were first registered in.