PRIME Minister Tayyip Erdogan pressed a widening purge of the police command yesterday, tackling what he describes as a foreign-backed conspiracy to undermine him and create a "state within a state".

The gathering crisis raised fears of damage to the Turkish economy and a fracturing in Mr Erdogan's AK Party, helping drive the lira to a historic low.

Yesterday saw 14 more senior officers removed over a series of anti-corruption raids and the detention of senior businessmen close to Mr Erdogan as well as sons of three cabinet ministers.

The powerful Istanbul chief was sacked on Thursday following the dismissal of dozens of unit chiefs.

"This is not one of those crises from which Erdogan can come out stronger," said Henri Barkey, a Turkey specialist at Lehigh University's department of international relations. "The public will ask if this is the result of an evil probe (or) foreign plot, then why are all of these police chiefs sacked?

"People will not forget the talk of money (found) at people's houses, and there will be a reflection of it at the ballot box."

Mr Erdogan has refrained from naming US-based Islamic cleric Fethullah Gulen, a man with strong influence in the police and judiciary, as the hand behind the raids which have shaken the political elite. But Gulen's Hizmet movement has been at odds with Mr Erdogan in recent months.

Mr Erdogan, who called the raids and detentions a "dirty operation" to tarnish the government, is under pressure to resolve the crisis before it hits the economy.

"The problem is this is not happening at a time when the economy is given enough of a buffer to withstand political turbulence. The fear is that the authorities start to loosen fiscal policy," said Manik Narain, strategist at UBS in London.