There has been no further comment from the governor. Deportations - even to war-ravaged Syria - were already under way in the days since the July announcement, say many Syrians and rights groups.
Istanbul has 547,943 Syrians under "temporary protection," according to Interior Ministry data. Experts say the governor's order could affect 300,000 unregistered Syrians.
Mehdi Davut, the head of the platform, told dpa the deadline could be extended by three months.
In either scenario, six centres will be set up in Istanbul for the migration authority to finger-print Syrians not registered anywhere in Turkey.
Davut said those registered in other provinces will be provided with transport to move with their belongings.
The first buses for Syrians are expected to leave Istanbul on Saturday, he said.
Excluded from the order are those families whose children are registered in Istanbul schools, businesspeople and orphans, he said.
More than 3.6 million Syrians escaping conflict were welcomed in Turkey and offered "temporary protection," which unlike full refugee status doesn't provide complete legal protection.
While many refugees remain in the Turkish provinces bordering Syria, most move westwards to Istanbul in search of work. They largely subsist in a shadow economy and form the cheapest labour force in sectors such as agriculture.
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