A heavy-handed police crackdown on Turkish protesters marking the one year anniversary of deadly anti-government demonstrations earned Ankara Sunday strong rebuke from the Council of Europe.

"I condemn the excessive use of force by the Turkish police against demonstrators and journalists," Nils Muiznieks, the Council of Europe commissioner for human rights, said in a statement sent to Agence France Presse.

A young man who was shot dead during last week's police crackdown on protesters in Istanbul was killed by a bullet fired from a policeman's gun, local media said Thursday.

Ugur Kurt, 30, died of gunshot wounds to the head after being caught in the crossfire during clashes between police and protesters in Istanbul's restive Okmeydani district.

EU foreign policy chief Catherine Ashton and Iran's Foreign Minister Mohammad Javad Zarif met behind closed doors Monday in Istanbul to discuss the path toward a final nuclear deal, an Iranian source said.

The previously announced two-day meeting comes after fruitless talks between Iran and world powers in Vienna earlier this month when no "tangible progress" was made ahead of a July 20 deadline for a comprehensive agreement.

Turkish police on Monday arrested at least 20 people across Istanbul for taking part in last week's deadly anti-government protests, local media reported.

Anti-terror police units, backed by helicopters, sealed off the restive district of Okmeydani where two people were killed during battles between law enforcement officers and protestors, NTV television channel reported.

Thousands of people from Turkey's minority Alevi community on Sunday held protests over the deaths of two people during a police crackdown on demonstrators earlier in the week.

Protestors flocked to rallies in Istanbul, Ankara and Izmir to call for an end to discrimination after two men were caught up in clashes between police and protesters in a predominantly Alevi district on Thursday and killed.

Ten thousand mourners marched through Istanbul on Friday to honor a man killed by crossfire in clashes between police and anti-government protesters, as fresh running battles the shook city's streets.

Riot police clad in heavy body armor used tear gas and water cannon to disperse crowds as rioters blocked roads and burned tires in the second day of demonstrations, said an Agence France Presse photographer on the scene. 

One man was injured when Turkish riot police on Thursday fired tear gas and water cannon to disperse a group of Istanbul protesters hurling Molotov cocktails and stones.

Tensions are high in Turkey with the approach of the first anniversary of deadly nationwide anti-government protests and in the wake of an unprecedented mine disaster that claimed 301 lives last week.

Riot police in Istanbul used water cannon and tear gas Thursday against thousands of protesters who tried to defy a May Day ban on demonstrations, injuring at least 50 people.

After a final warning, hundreds of riot police moved on the crowd seeking to breach the barricades leading to Taksim Square, declared off limits to Labour Day demonstrators as the epicenter of anti-government protests in recent months.

Turkey's secular opposition on Tuesday rejected the results of Ankara and Istanbul mayoral elections claimed as victories by the Islamic-rooted party of Premier Recep Tayyip Erdogan, citing "irregularities".

More than 1,000 people demonstrated outside the elections authority in the capital Ankara, where the incumbent mayor of Erdogan's ruling party has declared victory with a wafer-thin margin of about one percent.

Turkey's Premier Recep Tayyip Erdogan was to hit the home stretch of a campaign marathon Saturday on the eve of local elections, as police hunted those behind a spate of damaging online leaks.

Erdogan and his Islamic-leaning party, after over a decade in power, face the first electoral test following months of political turmoil, with mass street protests and a corruption scandal spread via Twitter, Facebook and YouTube.