Waving Turkish flags the protesters regularly shouted slogans such as "Turkey is secular and will remain so," and "This is Turkey, not Iran."

Some 50 non-government organizations, including many women's groups backed the protest, where representatives laid a wreath at the mausoleum of Mustafa Kemal Ataturk, founder of the modern Turkish republic, and sang the national anthem.

The Turkish parliament is due to vote next week on changes to the constitution that will allow women to wear headscarves to universities. The changes are expected to pass easily after the ruling Justice and Development Party (AKP) reached a deal with the far-right Nationalist Movement Party last week.

Opponents fear the Islamification of Turkey

The government has argued that the changes are a women's rights issue but opponents fear that the moves are part of a creeping Islamification of Turkish society and that the Islamic-rooted government of Prime Minister Recep Tayyip Erdogan ultimately seeks to impose sharia law.

On Saturday morning, Foreign Minister Ali Babacan said lifting the ban was a requirement for Turkey joining the European Union.

Establishment groups such as the judiciary, top business groups and academics have condemned the plan to lift the restrictions. The staunchly-secularist military has refused to get involved in the debate but has made it clear they are watching events carefully.

The opposition Republican People's Party has vowed to go to the Constitutional Court in an attempt to block the changes.

AKP election result leads to headscarf debate

Wearing of the headscarf in universities was first banned after the 1980 military coup but it was not until the late 1990s that the ban was strictly enforced. Rather than take off their head-coverings, many devout Islamic women have refused to go to university and some, including Erdogan's daughters, have studied abroad to get around the ban.

The move to allow the Islamic-style head-covering comes after Erdogan's AKP was returned to power last year in early elections that were forced following a series of spats with secularists over the nomination for the presidency of Abdullah Gül, whose wife wears a headscarf.