Turkish police have used tear gas to disperse demonstrators in Istanbul and Ankara on the first anniversary of deadly anti-government protests.
Some 25,000 police surrounded and blocked Istanbul's Taksim Square, the epicentre of the 2013 rallies.
PM Recep Tayyip Erdogan earlier urged youths to not join Saturday's protests.
Protests against plans to redevelop Gezi Park in Istanbul turned into mass rallies against PM Erdogan last year after a heavy-handed police response.
A number of people were killed in the unrest, with thousands more injured.
A 64-year-old woman, who fell into a coma after inhaling tear gas during another crackdown on protesters in the capital in December, died on Friday.
Clashes broke out in Istanbul on Saturday after protesters marched on Taksim Square despite a government ban on gatherings in force there.
Riot police, water cannon and armoured vehicles were deployed to block access to the square and nearby Gezi Park. A number of demonstrators were reportedly arrested.
Security forces also fired tear gas at demonstrators in central Ankara and broke up protests in the southern city of Adana.
Earlier on Saturday, Istanbul officers kicked and detained a CNN reporter during a live broadcast from Taksim Square.
Ivan Watson said in a Twitter post that he and his film crew were "released after half an hour".
The main organisers behind last year's Gezi Park protests - Taksim Solidarity - had called for a demonstration to mark the one-year anniversary.
But Mr Erdogan warned young people not to join, saying: "One year later, people, including so-called artists, are calling for demonstrations, but you, Turkey's youth, you will not respond to the call."
Addressing a crowd of young people in the capital on Friday, he described the movement as "terrorist organisations" that "manipulated our morally and financially weak youth to attack our unity and put our economy under threat".
At the scene - James Reynolds, BBC Istanbul correspondent
A year ago, protestors took the government by surprise and occupied Istanbul's Taksim Square and Gezi Park. This year, the government deployed thousands of police officers to seal off the square and the park - to prevent protesters from taking back the area. Lines of riot police guarded the streets leading up to the square. Plainclothes police officers, carrying batons and gas masks, sat on Gezi Park's benches.
At 1900, several hundred protesters on Istiklal - Istanbul's main shopping avenue - tried to advance towards Taksim Square. Within seconds, the riot police charged forward and fired tear gas. I saw officers take away a number of protesters.
Dozens of bystanders took refuge from the tear gas behind the glass doors of a music shop. Every few minutes the manager opened his doors to let in more people. Protestors booed a police helicopter overhead. After a while, many decided to walk away. They were unable to re-take Taksim Square.
String of scandals
Protesters have clashed with police in recent months, with two men killed during angry demonstrations over a mining disaster that killed 301 people.
Anger also flared in March with the news of the death of a 15-year-old boy who had been in a coma since last June after being hit by a tear-gas canister during a protest.
In May 2013, protesters took the government by surprise by occupying Taksim Square and Gezi Park.
Riot police evicted them two weeks later using heavy-handed tactics and galvanising anti-government demonstrators in several other cities.
Turkish media comment
Political commentator Guven Sak writes in Hurriyet: "Gezi was like a litmus test for all of us… Gezi is the "Basta moment" of the Turkish creative class... If you have any doubts about the impact of Gezi, just observe the number of policemen on the streets this weekend... Gezi freaked out the ruling elite of Turkey a year ago and look who is still freaking out. Just count the number of policemen."
(Via BBC Monitoring)
Since then, Mr Erdogan has faced accusations of authoritarianism and corruption after a string of scandals.
He has also moved to block social media sites YouTube and Twitter, after accusing his opponents of using them to deliberately undermine him.
In the first vote since last year's mass protests, Mr Erdogan's party won local elections in March, which were widely seen as a barometer reading of his popularity.