Hundreds of thousands of people have marched in Istanbul in defence of Turkey's secular system of government.
The demonstration was prompted by a row over the ruling party's candidate for Turkey's president, amid fears of a drift towards Islamist influence.
Turkey is a Muslim-majority country, but has been officially secular since Kemal Ataturk founded the republic in 1923.
One sign called for the candidate, Abdullah Gul, to stand down unless he distanced himself from his Islamic roots. The sign reads Goodbye Gul.
The police said as many as one million people took part in the demonstration.
Turkey's powerful military has already warned that any candidate must ensure a secular state.