Nearly 500 police officers were either fired or reassigned on Wednesday, local news outlets said, part of what appears to be a purge related to a graft inquiry that has already ensnared many of the prime minister’s allies. News reports said at least some of the reassigned officers took part in the large corruption investigation. Government critics fear the continuing changes in personnel — hundreds of police officers have already been purged — are meant to derail the investigation. Government officials insist, however, that the changes are legitimate efforts to eliminate what they call a “parallel state.” That refers to those in the judiciary and the police force loyal to a rival of Prime Minister Recep Tayyip Erdogan. Wednesday’s reshuffle followed the relocation on Tuesday of nearly 100 judges and prosecutors, a move made during Mr. Erdogan’s first visit in five years to Brussels, where he confronted European Union officials’ concerns about the separation of powers and a free judiciary in Turkey.