* Activists seek to commemorate deaths, year after protest
* Police fire teargas at protesters
* PM Erdogan calls demonstrators "pawns" (Adds detentions, injuries)
By Ayla Jean Yackley
ISTANBUL, May 31 (Reuters) - Turkish police fired teargas and water cannon on Saturday to disperse protesters in central Istanbul who sought to mark the one-year anniversary of the country's biggest anti-government demonstrations in decades.
Authorities closed roads and stopped public transport to deny access to Taksim Square and the adjoining Gezi Park where government plans to raze the green space and build a shopping mall sparked last year's unrest.
Police lines kept back activists who had hoped to read a statement at Taksim Square and lay flowers at the park to commemorate the deaths of at least six people in the protests against Prime Minister Tayyip Erdogan's rule.
Another half-dozen people died in sporadic unrest in the ensuing months as anger at Erdogan and his AK Party simmered.
Street protests could be a recurring feature in the run-up to an August presidential election in which Erdogan is expected to stand, but few expect this to cause the three-time premier serious political damage.
A senior AK Party official said on Saturday that Erdogan would run for the presidency and rule Turkey until 2023.
Near Taksim, hundreds of people chanted "Resign, murderer AKP" and "Everywhere is Taksim, everywhere is resistance" before police fired teargas at the crowd, forcing it to retreat.
Eighty people were detained and 13 were injured in clashes with police, Turkey's Human Rights Association said, but no official figures were immediately available. Police helicopters circled overhead.
Tourists lugging suitcases were forced to turn back to escape the stinging gas. A few hundred protesters carrying political banners ran away from police down a hill towards the Bosphorus Strait, the waterway bisecting Istanbul, Europe's biggest city with about 14 million residents.
Police also broke up protests in the capital Ankara and the southern city of Adana, CNN Turk reported.
"TRAITORS AND PAWNS"
In neighbourhoods across Istanbul, residents opened their windows and banged pots and pans, a traditional form of dissent that was employed throughout the Gezi protest.
Erdogan accused opponents of taking to the streets to push their demands but said a March 30 municipal election that his party won decisively means he had been authorised to fight back.
"I want my people to see clearly that young people were used as pawns by internal and external traitors in the Gezi incidents," he said in a television address. "On March 30, you authorised us to fight against these traitors and pawns."
On May 31, 2013, police forcefully evicted environmentalists from Gezi Park who had staged a peaceful sit-in for several days to try to stop government plans to erect a shopping centre and luxury flats in one of central Istanbul's few remaining parks.
Angered by the use of violence, tens of thousands of people from a variety of political backgrounds descended on Gezi and occupied Taksim Square for two weeks before authorities finally cleared the space.
Many at Gezi complained of authoritarianism as Erdogan, a religious conservative who dominates the Turkish political scene, marked a decade in office.
Turkish newspapers said 25,000 officers were deployed on Saturday. Riot police circled the perimeter of Gezi, and hundreds of plainclothes officers carrying batons patrolled nearby streets.
The metro station at Taksim was closed and the governor halted ferryboat services between Istanbul's shores on either side of the Bosphorus Strait.
Elif Cetinkaya, 45, and her family gathered across the street from Gezi Park in a quiet protest, wearing T-shirts with the images of those killed in the 2013 unrest.
"Why did so many people have to die to save this park? We are here to mourn their loss and show that we stand firm, no matter what obstacles they erect," Cetinkaya said.
But the movement has lost much of its momentum since the March vote, said a member of a leftist party who wore a scarf to ward off teargas.
"After the election, many people felt nothing made a difference. There's no one issue now for everyone to rally around," he said, requesting anonymity. (Additional reporting by Humeyra Pamuk, Ece Toksabay and Nicholas Tattersall; Editing by Robin Pomeroy and Pravin Char)