Turkish riot police Saturday used tear gas grenades and water cannon to disperse more than 2,000 people demonstrating against new Internet curbs that have sparked alarm at home and abroad.

Large numbers of police with body armour and shields backed up by armoured water cannon trucks deployed against the chanting, mostly young crowd around Istanbul's emblematic Taksim Square.

"I pay my own Internet bill but it's the government that decides what sites I can look at," one demonstrator, Semih, complained to AFP.

"They want to control what we do on the Internet. It's repression. But the young will not be repressed, we won't take it lying down."

Protestors threw stones at police, smashed windows including at a US fast food outlet and sprayed anarchy signs on banks, pursued by police down side streets off the central Istiklal boulevard.

Earlier Saturday, Prime Minister Recep Tayyip Erdogan vehemently rejected criticism of the new curbs, passed on Wednesday by parliament, to a crowd of several thousand supporters in Istanbul

"These regulations do not impose any censorship at all on the Internet.... On the contrary, they make it safer and freer," Erdogan said, denying that authorities would now have access to Internet users' personal information.

"Never. It is out of the question that people's private data will be recorded," said Erdogan, who has been in power since 2003.

The new curbs provoked a storm of consternation, with critics saying they were an attempt by Erdogan to stifle dissent and stop evidence of high-level corruption being seen online.

They give the telecoms authority the power to order a webpage blocked without the need for a court order if the content is deemed to infringe privacy or is offensive.

The timing in particular raised eyebrows because it comes as Erdogan deals with a major graft scandal that erupted in December, implicating his inner circle.

- Government trying 'to silence critics' -

Human Rights Watch said the restrictions raise concerns that a "defensive government is seeking to increase its power to silence critics and to arbitrarily limit politically damaging material online".

European Parliament chief Martin Schulz called them a "step back in an already suffocating environment for media freedom," while Washington also expressed misgivings.

Erdogan has portrayed the investigation as a plot against him by people within the Turkish police and judiciary loyal to Fethullah Gulen, an Islamic preacher living in the United States.

His government has sacked or moved to different jobs thousands of police and prosecutors ahead of important local elections on March 30 which could determine whether he runs for president in August.

"One of the few remaining liberties we have is the Internet and being able to communicate. This is what they want to constrain," said Burak, another young demonstrator in Istanbul.

"They are really scared of social networks and the Internet."

Erdogan, 59, is also seeking to push through legislation reforming the judiciary, which critics will say will increase government control, and there are also worries for the freedom of the press.

On Friday an Azeri journalist and blogger was deported from Turkey because of tweets criticising the government, according to his newspaper, Zaman, which is close to Gulen.

The Organisation for Security and Cooperation in Europe (OSCE) said that Mahir Zeynalov's ejection "is a further setback for the dire state of media freedom in Turkey".

US-based rights group Freedom House said that over the past year "dozens of journalists have been fired because of government pressure, and government officials' threats against journalists have become common".