Turkey's combative prime minister warned protesters that police would do "whatever is necessary" to clamp down on demonstrations Saturday in Istanbul's Taksim Square to mark the anniversary of last year's turmoil.

As police deployed some 25,000 officers as well as dozens of water cannon trucks and armored vehicles to prevent demonstrators from reaching the square, Recep Tayyip Erdogan vowed tough anti-protest measures.

"I am calling on all my people. Do not be deceived. This is not an environmentalist campaign. There is no sincerity here," 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.

His address was often interrupted by loyalist slogans of "Turkey is proud of you!"

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.

Despite a ban this year on protests at the square, activists called for a new rally, raising the specter of fresh clashes after police confronted demonstrators trying to defy a similar ban on May Day.

"Despite these policies of violence and injustice, we will be on the streets," vowed Mucella Yapici, founding member of the activist group Taksim Solidarity.

"The government maintains a tense atmosphere that encourages police violence," she charged.

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."

Police blocked streets Saturday leading up to Taksim Square and public transportation to the square was halted. According to local media, Bosphorus ferry services were cancelled.

"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 the 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."

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."

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 run 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.

Raising the tensions ahead of the anniversary, opposition supporters were mourning the loss of a 64-year-old who had fallen into a coma during a crackdown on protesters in December.

She died on the eve of the anniversary.

Tayfun Karaman, member of the Taksim Solidarity group, vowed they would not bow to violence.

"The government is dealing with us in an increasingly violent way. We don't have any other choice, the only way for us to be heard is to demonstrate in the street," he told AFP.

"That's the only arena that is left to us ... We are not going to give up our fight, we will keep on resisting".