Turkish President Recep Tayyip Erdogan¡¯s main political opponents have faced an unprecedented crackdown that has seen more than 500 detained in just nine months, according to a review of a sprawling investigation that has accelerated dramatically in recent days.

Erdogan says the probe tackles what he calls a corrupt network that is like ¡°an octopus whose arms stretch to other parts of Turkey and abroad.¡±

The investigation, which began in Istanbul but has spread across the country, has targeted only municipalities run by the main opposition Republican People¡¯s Party (CHP), the party of modern Turkey¡¯s secularist founder Mustafa Kemal Ataturk.