Rallies supported by 600 non-governmental organizations were held in the Turkish capital Ankara and largest city of Istanbul on Sunday to show their support for the country's secular system.
Carrying Turkish flags, the demonstrators shouted slogans to protect the country's secularism and principles of Mustafa Kemal Ataturk, the founder of modern Turkey.
Local media said the rallies are expected to draw tens of thousands people.
The rallies, similar to the April 14 mass demonstration in Ankara, came amid mounting tension stemming from the presidential elections between the Islamic-rooted ruling Justice and Development Party (AKP) and the country's secularists.
Turkish Foreign Minister Abdullah Gul, presidential candidate of the ruling Justice and Development Party (AKP), failed to garner the required two-thirds majority of 367 votes in the first round of voting on Friday.
The main opposition secularists Republican People's Party (CHP), which boycotted the vote, appealed to the country's constitutional court to annul the presidential vote since the parliament convened with less than 367 lawmakers to elect the new president.
If the court upholds the CHP's appeal, a scheduled general election in November, will be called within 90 days. Otherwise, Gul will be elected as the new president in a third round of voting on May 9, when 276 votes will be sufficient.
Late on Friday, the staunchly secularist Turkish army issued a statement, saying that it was watching with concern the debate over the secular system in the presidential elections and would "openly display its position and attitudes when it becomes necessary."
The Turkish government on Saturday criticized the army's threat to defend the country's secularism by intervening in domestic politics.
Gul, a close ally of Prime Minister Recep Tayyip Erdogan, told a news conference on Sunday that he would not retreat from the elections.
"The process is going on. We should all wait for the decision of the Constitutional Court," Gul affirmed.
"As the issue is on the agenda of the court at the moment, it will not be right to express any opinions. The court will take the accurate decision and we should all respect that," Gul added.
(Xinhua News Agency April 30, 2007)