Turkish police has detained 20 people as part of an investigation into an alleged planned military coup against the government, daily Hurriyet reported on July 1.

The arrests come on the same day that chief prosecutor Abdurrahman Yalcinkaya was due to present his case in the suit filed with the Turkish constitutional court, asking for the country's ruling Justice and Development (AK) party to be disbanded and a number of its top officials to be banned from politics for a period of five years.

Among those detained are two prominent retired generals, two journalists and the chairperson of Ankara's chamber of commerce, according to Hurriyet. "The common point of those names is that they are among the fiercest opponents of the government," the daily said.

The arrests are part of what has been called the Ergenekon operation, an investigation into an ultra-nationalist secularist group accused of planning to overthrow the government. "I think these detainments are a step forward to conclude the indictment of the case," Turkish Prime Minister Tayyip Erdogan said, as quoted by Hurriyet.

Opposition parties and political analysts have blamed the government of using the investigation to go beyond its initial targets and using it as a means to suppress the government's critics.

Secularists fear that the AK, with roots in political Islam, harbours a long-term agenda of undermining Turkey's secular constitution, put in place by Kemal Ataturk, a charge that the AK denies.