Turkish journalists Nedim Sener and Ahmet Sik have appeared in court with 11 other defendants to face conspiracy charges they say are politically motivated.

The defendants, most of them journalists, have been linked with a group allegedly attempting to overthrow the country's Islamic-based government. They began their defense on Thursday.

Sener told reporters the real reason he is on trial is because he wrote a book criticizing the government.

Sener and Sik have been in prison since March. They are among hundreds of people, including academics and retired and serving senior military officers, on trial in an investigation of the secularist network, Ergenekon.

Prosecutors say the group plotted in 2003 to discredit and bring down the government through bombings and other attacks to trigger a military coup against the ruling Justice and Development Party.

Turkish authorities have detained more than 300 people as part of a wide-reaching investigation. The case has highlighted international concerns about press freedom in Turkey.