Turkish police fired tear gas and water cannon at hundreds of people in Istanbul and Ankara Saturday as demonstrations marking a year since deadly anti-government protests erupted in fresh violence.
Police clashed with protesters near Istanbul's iconic Taksim Square, scene of last year's unrest that claimed eight lives and left thousands injured, an AFP reporter on the ground said.
"Everywhere is Taksim, everywhere is resistance," the demonstrators shouted.
Riot police also deployed tear gas and water cannon to disperse some 1,000 people in the capital Ankara, who hurled fireworks.
In the run-up to the anniversary, Turkey's prime minister had warned authorities would do "whatever is necessary" to curb protest.
"I am calling on all my people. Do not be deceived. This is not an environmentalist campaign. There is no sincerity here," Recep Tayyip Erdogan told thousands of supporters at an Istanbul rally.
"If you go there, our security forces have received clear-cut instructions and will do whatever is necessary from A to Z," said the premier.
"You will not be able to take to (Taksim) like you did last year because you are obliged to abide by the laws... If you do not, the state will do whatever is necessary for its security," he warned.
Security was tight around Taksim Square and other points in Istanbul, with some 25,000 police deployed, streets to the square blocked and public transport curtailed.
Pressure on the international media was also high amid a tense climate around Taksim. Police briefly detained a CNN team in the middle of a live report in the square.
"Turkish police released CNN team after half an hour. Officer apologised for another officer who kneed me while I was being detained," CNN's Ivan Watson wrote on Twitter.
Authorities said 65 people had already been arrested.
Last year, what started as a small campaign to save the nearby Gezi Park from the bulldozers eventually drew an estimated three million protesters in an outpouring of anger at the perceived authoritarian tendencies of Erdogan's Islamic-rooted government.
Eight people died and thousands were injured in the ensuing violence as police launched a brutal crackdown, frequently employing tear gas and water cannon.
Istanbul governor Huseyi Avni Mutlu said this week: "We know what happened in June last year and it is not a good memory ... We do not want to see such sorrow again."
But activists defied the ban on protests, with Mucella Yapici, founding member of the activist group Taksim Solidarity, vowing "we will be on the streets" despite what she called the government's "policies of violence and injustice".
"I am trying to remember all the voices and the sounds I heard here last year. You can't erase those memories," 41-year-old Sebnem, an actress, said early Saturday before Gezi Park was closed.
Ugur, 31, a teacher, said: "We will long remember all the people who lost their lives here, as well as the way our state behaved."
Earlier in Ankara, a group of protesters lit candles, released pigeons and lay carnations on the ground at Guven park, where 26-year-old Ethem Sarisuluk was shot in the head by police last year.
Last year's deadly protests turned into the largest challenge to Erdogan since his party came to power in 2002.
"It has been a year since the Gezi events erupted," Deputy Prime Minister Bulent Arinc said Saturday. "This is not something to commemorate or to be proud of".
"There are lessons that we have learned," he said without elaborating. "I don't want such events to happen again as they do not serve Turkey's peace, progress and strength."
One year on, the political tensions stemming from the Gezi revolt continue to simmer despite a decisive ruling party victory in March 30 local elections that has boosted Erdogan's ambitions to stand for president in August.
A succession of crises over the last 12 months -- from a government corruption scandal implicating the premier and key allies to the mine tragedy that killed 301 workers earlier this month -- have sparked renewed anger at Erdogan's leadership.
Critics meanwhile accuse Erdogan of pressing ahead with controversial policies including muzzling the press, tightening the government's sway over the judiciary and curbing the Internet.
"Turkish authorities have launched a witch-hunt against all those who have demonstrated or raised their voices," charged Karim Lahidji, president of the International Federation for Human Rights.
Last week, two people died in a working-class district of Istanbul after clashes between police and demonstrators who were commemorating the death of a teenage boy from injuries sustained during last year's unrest.
Tayfun Karaman, member of the Taksim Solidarity group, vowed they would not bow to violence.
"We are not going to give up our fight, we will keep on resisting," he told AFP.