However, results indicated that the Justice and Development Party of Prime Minister Recep Tayyip Erdogan was not heading for a two-thirds majority in Parliament, a shortcoming that would force it to seek support for constitutional change from other political groups.

With 97 percent of votes counted, Erdogan's party had won 50 percent of the votes, TRT reported. It said the Republican People's Party, the main opposition group, had 26 percent of the vote.

TRT said another opposition party, the Nationalist Action Party, had 13 percent of the vote, signaling it could stay in Parliament by crossing a 10 percent vote threshold designed to keep out smaller parties.

According to the tally, the ruling party stood to win 327 seats in the 550-seat parliament, a comfortable majority that would ensure the continuation of its single-party rule. It had 331 seats in the outgoing parliament.

Lawmakers serve four-year terms.

Several thousand supporters gathered Sunday night outside the ruling party headquarters in Ankara, chanting pro-government slogans and waving Turkish flags as they awaited Erdogan, who has made it a tradition to deliver a victory speech from the building's balcony.

About 50 million Turks, or two-thirds of the population, were eligible to vote.

For the first time, voters cast ballots in transparent plastic boxes in which the yellow envelopes could be seen piling up. The measure was designed to prevent any allegations of fraud. In past elections, wooden boxes were used.

"We have spoken, and now it is time for the people to speak," Erdogan said at a polling station Sunday morning in Istanbul. "For us, this will be the most honorable decision and one that we will have to respect."