A Turkish court has banned media from reporting on a parliamentary investigation into corruption allegations against four ex-ministers, a move the opposition says amounts to protecting thieves.

Tayyip Erdogan, then prime minister and now president, has called the corruption scandal this year a plot to unseat him. Courts have since dropped cases, including those against the sons of three ministers and businessmen close to Erdogan.

A copy of Tuesday's ruling, seen by Reuters, said the ban was imposed to "prevent damage to the individual rights" of the former economy, interior, EU affairs and environment ministers.