Chants such as "Turkey is secular and will remain secular" could be heard from the marchers who gathered in a city center square under the watch of thousands of police officers.

Sunday's protests were organized by the Kemalist Thought Association (KTA), an organization dedicated to preserving the legacy of Mustafa Kemal Ataturk (1881-1938), the founder of the modern Turkish republic.

The marchers were waving red and white Turkish flags and were headed for the mausoleum of Ataturk, the traditional rallying point of those in favor of secular rule.

Qualms with Prime Minister

The demonstrators protested what they called the anti-secular principles of Prime Minister Recep Tayyip Erdogan. His opponents accuse him of attempting to make Turkey more overtly Islamic through incremental steps, such as failing to end bans on Islamic-style headscarves at Turkish universities.

Protestors also accused the AKP of seeking to replace Turkey's secular system with a regime based on Sharia, or Koranic law.

The AKP does have religious roots but has rejected being referred to as "Islamist".

Secularists are concerned about the rise of Erdogan's Justice and Development Party (AKP), and the election by the AKP-controlled parliament of Abdullah Gul as president.

Demonstrators were also protesting the government's handling of the economy as unemployment in the country has reached a record high amid the global economic downturn.

glb/AFP/Reuters
Editor: Andreas Illmer