Incumbent candidates from Erdogan's Justice and Development Party, better known by its Turkish acronym AKP, were also leading in high profile races in Istanbul and Ankara, according to the early results. Voter turnout appeared to be heavy, with people forming long queues at polling stations.
The strong results would appear to strengthen the prime minister following a tumultuous corruption scandal. In recent days, Erdogan has also provoked outrage at home and abroad by blocking access to Twitter and YouTube.
The result could also embolden Erdogan to run for president in an election scheduled for August. Prior to Sunday's showing, he had appeared to be leaning against that route, which has risks. In a direct vote, he would have to win 50 percent in a country that is deeply polarized over his rule.
Erdogan and his party have dominated Turkish politics over the past decade in a period of great prosperity. His party came to power backed by a pious Muslim base looking for greater standing in a country that had for decades favored a secular elite. But AKP, whose party symbol is a light bulb, has also cultivated an identity of pragmatism and competency.
That image has been rocked by the corruption scandal, with a series of leaked tapes bringing down four ministers with revelations of bribe-taking and cover-ups. One tape allegedly involves Erdogan and family members, but he and his allies have rejected the allegations as a plot orchestrated by followers of U.S.-based Muslim cleric Fethullah Gulen, a former Erdogan ally who has split with him.
In the wake of the scandal, Erdogan has shuffled thousands of police officers and tightened control of the judiciary, which had launched investigations. The moves prompted concern that Erdogan was moving toward more authoritarian rule.
But in his victory speech, Erdogan said that democracy in Turkey is strong:
"We have the democracy which the West is longing for," he said.
Suzan Fraser in Ankara contributed to this report.