Although the ruling party's success has been touted as proof that Islam and democracy can coexist, the new government is likely to face persistent tension over the role of Islam in society.

State-run Anatolia news agency was projecting that Prime Minister Recep Tayyip Erdogan's Justice and Development Party would win 340 of the 550 seats, as votes in all but six of more than 158,000 ballot boxes across the country were counted.

Erdogan, a devout Muslim, pledged to safeguard the country's secular traditions and do whatever the government deems necessary to fight separatist Kurdish rebels.

"We will never make concessions over the values of people, the basic principles of our republic. This is our promise. We will embrace Turkey as a whole without discriminating," he said at a rally in the capital, Ankara.

European Commission President Jose Manuel Barroso congratulated Erdogan's victory.

"This comes at an important moment for the people of Turkey as the country moves forward with political and economic reforms," Barroso said in a statement.

The EU chief said that Erdogan "has given his personal commitment to the sustained movement towards" the EU.

The 27-nation bloc, while divided over whether Turkey should one day join the club, continues to spur Ankara to continue reforms to keep on track its membership bid.

Ruling party supporters clapped, danced and waved flags depicting the party symbol, a light bulb, outside the party's office in Istanbul. In Ankara, hundreds whooped as they watched election results on a big TV screen set up outside party headquarters.

"We are very happy," university student Reyhan Aksoy said. "God willing, great days await us."

The election was called early to defuse a showdown with the military-backed, secular establishment, which contended that Erdogan and his allies were plotting to scrap Turkey's secular traditions despite their openness to the West.

Erdogan raised concern with his efforts as prime minister to make adultery a crime and appoint former Islamists to key positions. Critics also were troubled by his calls for the lifting of restrictions on the wearing of Islamic headscarves.

The government will have to decide how to deal with violence by Kurdish rebels seeking autonomy. Nato member Turkey is considering whether to stage an offensive into northern Iraq against separatist Kurdish rebels who rest, train and resupply at bases there.

Erdogan has warned the incursion could happen if security talks with Iraq and the US fail. He has invited Iraqi Prime Minister Nouri al-Maliki to visit Turkey.

"In our struggle against separatist terrorists, we are determined to take every step at the right time," Erdogan said of the conflict with the Kurds.