UPDATE 6-Erdogan facing major test as voting ends in Turkey elections
* New powerful presidency comes into effect after polls
* Erdogan facing strong challenge from opposition's Ince
* Ince urges Turks to protect ballot boxes against fraud
* Turkey has growing economic woes, security threats (Adds opposition candidate Ince's comments, paragraph 8, edits)
ISTANBUL, June 24 (Reuters) - Turks voted on Sunday in presidential and parliamentary elections that pose the biggest ballot box challenge to Tayyip Erdogan and his Islamist-rooted AK Party since they swept to power more than a decade and a half ago.
The vote also ushers in a powerful new executive presidency long sought by Erdogan and backed by a small majority of Turks in a 2017 referendum. Critics say it will further erode democracy in the NATO member state and entrench one-man rule.
Polling stations closed at 5 pm (1400 GMT). Turnout was good, President Erdogan said, as is customary in Turkey. There were no exit polls and the first results were expected later in the evening.
Polls show Erdogan falling short of a first-round victory in the presidential race. He would be expected to win a run-off on July 8, while his AK Party may lose its parliamentary majority.
Earlier, a crowd of Erdogan's supporters chanted his name as he emerged from a school after voting in Turkey's largest city Istanbul, shaking hands with people amid tight security.
"Turkey is staging a democratic revolution," he told reporters in the polling station. "With the presidential system, Turkey is seriously raising the bar, rising above the level of contemporary civilisations."
Erdogan, the most popular but also divisive leader in modern Turkish history, argues the new powers will better enable him to tackle the nation's economic problems - the lira has lost 20 percent against the dollar this year - and deal with Kurdish rebels in southeast Turkey and in neighboring Iraq and Syria.
But he reckoned without Muharrem Ince, the presidential candidate of the secularist Republican People's Party (CHP), whose feisty performance at campaign rallies has galvanized Turkey's long-demoralized and divided opposition.
Voicing opposition concerns about possible electoral fraud, Ince told reporters outside the High Electoral Board (YSK) after polling stations had closed that citizens should protect ballot boxes. He also urged YSK members to "do your job the right way," adding he believed the results would be "very good."
Opposition parties and NGOs deployed up to half a million monitors at ballot boxes to ward against fraud. They have said election law changes and fraud allegations in the 2017 referendum raise fears about the vote's fairness.
Earlier, CHP spokesman Bulent Tezcan said the party had reported to the YSK allegations of block votes being cast and of election monitors being beaten and kept out of polling stations in the southeast's Sanliurfa province.
YSK chairman Sadi Guven told the state-owned news agency Anadolu it was taking steps in response to reports of irregularities in the town of Suruc near the Syrian border.
The government gave no immediate response to the reports, but Erdogan said there had not been any serious problems.
Turkey has been under emergency rule - which restricts some freedoms and allows the government to bypass parliament with decrees - for nearly two years since an attempted coup in 2016.
Erdogan blamed the coup on his former ally, U.S.-based Muslim cleric Fethullah Gulen, and has waged a sweeping crackdown on his followers in Turkey, detaining some 160,000 people, according to the United Nations.
The president's critics, including the European Union which Turkey still nominally aspires to join, say Erdogan has used the crackdown to stifle dissent.
Ince told a rally on Saturday he would lift the state of emergency within 48 hours of being elected president. He also vowed to reverse what opposition parties see as Turkey's swing towards authoritarian rule under Erdogan.
"This is no longer a Turkey we want. Rights are violated, democracy is in terrible shape," said health sector worker Sema, 50, after voting in Istanbul.
She and others in the city said they voted for the pro-Kurdish Peoples' Democratic Party (HDP), hoping it would exceed the 10 percent threshold of votes needed to enter parliament. If it does so, it will be harder for the AKP to get a majority.
(Additional reporting by Gulsen Solaker, Tuvan Gumrukcu, Ali Kucukgocmen, Ezgi Erkoyun and David Dolan; Writing by Gareth Jones; Editing By Jon Boyle)
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