The court ruled that the 550-seat parliament should have convened with at least 367 deputies -- or the two-thirds majority needed for a president to be elected in the first round -- for the voting to have begun, the court's vice president Hasim Kilic told reporters.

According to parliamentary minutes, 361 lawmakers were present in the assembly on Friday.

The petition challenging the procedure was filed by the main opposition party, the social-democratic Republican People's Party.

"It is now up to parliament to decide how to proceed," Kilic said, adding that parliament could begin the election process anew.

Early elections urged

Gul urged speedy early legislative polls if parliament fails to elect him in a repeated vote.

"Let us see if the lawmakers have changed their minds after all these developments," Gul said in an interview broadcast on TRT state-television.

"The number (of lawmakers in support of his presidency) may increase or decrease, but, after that, my personal opinion is to call... elections at the earliest possible time," he said.

The ruling came amid a tense standoff between the secularist military and the ruling Islamist-rooted Justice and Development Party (AKP), whose Foreign Minister Abdullah Gul was the sole candidate in the presidential election.

The Turkish constitution orders general elections if parliament fails to elect a president in up to four rounds of voting. General elections are currently scheduled for November 4.

According to media reports, Prime Minister Recep Tayyip Erdogan and his aides have already discussed bringing the November 4 elections forward to sometime between the end of June and early August.

Secularists worry

Early elections are generally seen as a way out of the current crisis, which erupted over the prospect of the AKP-dominated parliament electing a president with an Islamist background.

Secularists say the AKP, the moderate offshoot of a now-banned Islamist party, is not truly committed to Turkey's fiercely guarded secular system and Gul's presidency would erode the separation between state and religion.

Opposition parties, who had been pressing for early elections for months, boycotted the first-round vote on Friday.

Hours after the balloting, in which Gul fell just 10 votes short of being elected, the influential Turkish army accused the government of failing to stop rising Islamism in the country and warned that it would act to protect the secular system if necessary.

The extraordinarily harsh statement was widely seen as an indication that Gul is unwelcome as president.

About one million people demonstrated in Istanbul at the weekend in favor of secularism and against Gul's presidential ambitions.