By Selcuk Gokoluk and Ibon Villelabeitia

ANKARA, Turkey (Reuters) - Turkish Prime Minister Tayyip Erdogan's ruling AK Party was heading for a clear victory in Sunday's local elections after nearly a quarter of the vote had been counted, according to private broadcasters.

The AK Party won 40.6 percent of the vote in provincial assemblies, CNN Turk and NTV said, a result that would hand Erdogan a fresh mandate to press on with political and economic reforms in the European Union candidate country.

The vote for mayors and municipal and provincial assemblies was marred by violence after five people were killed in the mainly Kurdish southeast as rival supporters for non-party village chief posts clashed, security and hospital sources told Reuters. Nearly 100 people were wounded in the violence.

In 2007 the Islamist-rooted AK Party won 47 percent of the vote in a parliamentary election and Erdogan had hoped to secure at least the same figure on Sunday despite high unemployment and a worsening economy.

The municipal elections were largely seen as a referendum on Erdogan's rule and the projected results, if confirmed, would be a sharp contrast to the backlash against elected governments in Eastern Europe amid the global financial crisis.

The southeast is one of the main battlegrounds of the elections because Erdogan hopes to wrest the region from pro-Kurdish parties in what might prove a historic step toward solving a deadly conflict weighing heavily on the country's economic and political development.

The AK Party, rooted in political Islam but also embracing nationalists and center-right elements, was nearly closed down by the Constitutional Court for Islamist activities in a 2008 case that rattled financial markets and deeply polarized Turkey.

Erdogan has pledged to reform the constitution drafted by the military in 1982 and change the way the Constitutional Court works -- steps which would remove some obstacles to EU membership but could revive tensions with secularists who accuse him of pursuing an Islamist agenda. Erdogan denies this.

The IMF and Turkey have been in talks for months on a deal markets say is key to shielding the $750 billion economy from the global crisis. Markets expect Erdogan to complete those talks after Sunday's vote.

Turkey's unemployment rate is at an all-time high and the once-rapidly economy is likely to contract in 2009. But the opposition seems to have failed to capitalize on the crisis because it is not seen a viable alternative to carry out political reforms and manage the economy.

(Additional reporting by Alexandra Hudson in Diyarbakir; editing by Matthew Jones)