Turkish Prime Minister Tayyip Erdogan's government purged hundreds of police officers overnight, media said, as part of a crackdown on a rival he accused of trying to usurp state power by tarring him with a specious corruption investigation. Some of the officers, who included members of the financial and organised crime, smuggling and anti-terrorism units, were moved to traffic duties, according to the reports. Ankara police, the chief focus of the action, declined to comment. Despite the dismissals, among them senior commanders, police and prosecutors continued arrests, which yesterday targeted the state railway company and a western port. Erdogan, facing the biggest challenge of an 11-year rule that has seen the army banished from politics, the economy booming and Ankara pressing its role in the Middle East, portrays the raids and arrests as a "dirty plot" by US-based cleric Fethullah Gulen, who backs no political party but exercises broad, if covert, influence in the Turkish police force and the judiciary. Details of the accusations have not been made public but are believed to relate to corruption in construction and real estate projects and Turkey's gold trade with Iran, according to Turkish newspaper reports, citing prosecutors' documents. Prominent business people, the sons of three cabinet ministers and state officials are among those detained for questioning. The government has hit back by sacking or reassigning hundreds of police across the country since the crisis broke with a day of raids and arrests on December 17. A second investigation into infrastructure projects championed by Erdogan, including a rail tunnel beneath the Bosphorus strait linking the European and Asian sides of Istanbul, has been blocked by the government. According to the Hurriyet newspaper, some 1,700 police have been dismissed or reassigned in Istanbul and Ankara.