Sunday's election was a quasi referendum on whether to endow President Recep Tayyip Erdogan's office with powers that would alter Turkey's democratic process and prolong his period as the country's most powerful politician.

Erdogan's ruling Justice and Development Party (Turkish AKP) is expected to win significantly more votes than any opposition party, but it must win an absolute majority of the 550 seats in parliament to change the constitution.

However, all eyes will be on the results for the main Kurdish party, HDP. If it crosses a 10 percent threshold for entering parliament as a party, that would squash the AKP's constitutional plans.

Onerous campaign

The vote comes amid high tensions, after bombings on Friday during a HDP rally killed two people and wounded scores. On Sunday, Prime Minister Ahmet Davutoglu said a suspect had been detained in the case, but provided no further details.

More than 53 million voters in Turkey and abroad are eligible to choose the deputies to the Grand National Assembly. If the ruling AKP wins a majority of 330 seats, it could call for a national referendum to change the constitution. If the party captures 367 seats, it could vote in a change without a referendum.

After casting his vote, HDP leader Selahattin Demirtas called for peace after what he saw as an "onerous and a troubled campaign."

Aside from the constitutional issues, the election could have a major impact on the peace process to end decades of insurgency by Kurdish militants in Turkey.

Scuffles between rival party supporters were reported in at least two provinces Sunday, including one in Sanliurfa which injured 15 people.

Erdogan has been Turkey's dominant politician since his party swept into power in 2002 - becoming prime minister in 2003 and leading his party to two overwhelming parliamentary election victories. In a gamble last year he decided to run for president, banking that his party could later bolster his powers.

Under the current constitution, Erdogan is meant to stay above the political fray as president. But he has been campaigning vociferously, drawing complaints from the opposition that he is ignoring the constitution.

Power struggle

As he cast his vote Sunday, Erdogan praised the election as an indication of the strength of democracy in Turkey.

"This strong democracy will be confirmed with the will of our people and extend the trust we have in our future," he said.

Early in the campaign, he called on voters to give AKP 400 deputies, but a slim majority for the ruling party is a more likely result. That could leave Erdogan stranded in the presidential palace without the powers he has long sought.

A narrow win by the AKP, however, could be the best result for Davutoglu, who would lose power if Erdogan has his way.