Nearly all the politicians in Turkey's governing party have boycotted a presidential reception marking the republic's 80th anniversary in a row over Islamic-style headscarves.
A presidential wreath was laid at the mausoleum of Ataturk
Members of the Justice and Development Party, which has its origins in a banned Islamist movement, were angry at President Ahmet Necdet Sezer's refusal to invite any headscarf-wearing wives of senior officials, including Prime Minister Recep Tayyip Erdogan, to the event.
Headscarves - seen by the secular Turkish establishment as symbols of radical Islam - are banned in official ceremonies and in public buildings such as schools and courtrooms.
Mr Erdogan and his cabinet ministers did attend the reception, but the overwhelming majority of the party's 367 parliamentarians stayed away.
The official national day reception was held as part of celebrations to commemorate the founding of the Turkish republic by Mustafa Kemal, better known as Ataturk.
The BBC's Nick Thorpe in Istanbul says the anniversary is being taken as an opportunity by many to assess the progress that has been made towards resolving the deep internal contradictions which have riddled the past decades.
But our correspondent says the main debate within Turkey is over how the Justice and Development Party is squaring its pro-Islamic values with the fiercely secular state founded by Ataturk 80 years ago.
Several factors have combined to give this year's anniversary an added importance - the continuing violence in neighbouring Iraq, the election one year ago of a pro-Islamic government in Ankara and intensified efforts to join the European Union.
The Turkish Parliament has already agreed in principle to send troops to Iraq.
The arrangement appeared to satisfy both Turkey - which is keen to regain its former regional influence - and the United States which welcomed the idea of a moderate Muslim country sharing some of the security burden.
But the plan has been delayed and may even be shelved because of opposition by the Iraqi Governing Council. US officials have now asked the Turks to negotiate directly with the Iraqis.
The latest benchmark for relations with the European Union will become visible next week, when the EU publishes a report on Turkey's progress towards fulfilling the criteria for accession.
An EU decision on when such talks might begin is expected in December next year.