Hundreds of Turkish police have stormed Istanbul's Taksim Square, the site of ongoing demostrations against the government.

Reuters news agency quoted witnesses as saying on Tuesday that police, backed by armoured vehicles, fired teargas to scatter small groups of protesters who have been occupying the square against plans to redevelop an adjoining park.

However, the governor of Istanbul, Huseyin Avni Mutlu, said on Twitter that police were there only to remove banners and placards.

The police, wielding shields, moved past barricades set up by the protesters in Taksim Square, and blocked all exits.

Police fired water cannons and teargas in response to hails of stones, Molotov cocktails and fireworks from protesters.

Al Jazeera's Hashem Ahelbarra, reporting from the square, said that protesters outside the area were trying to converge on Taksim.

A statement from Mutlu's office said the aim of the invervention was to remove the banners of various groups in the square, which were making it look as though it was under "occupation". This was "negatively affecting our country's image in the eyes of the world opinion and leading to reaction from within the society".

The protest against the redevelopment of Gezi Park escalated into nationwide demonstrations against the government of Prime Minister Recep Tayyip Erdogan.

Al Jazeera's Emre Rende said police claimed they were not targeting those who were there to resist the redevlopment of Gezi Park. He said police were repeating this statement on loudhailers: "People in Gezi Park, we will not hurt you or intervene. We want to help you", while telling protesters in Taksim Square to "stop throwing stones, stop throwing bottles and we will stop the teargas".

Al Jazeera's Anita McNaught, reporting from Ankara, said she could understand the tactics to catch the protesters off-guard. However, "we had a statement from the government a couple of days ago saying there would not be a move on the protesters in Gezi Park and Taksim Square."

Erdogan has taken a defiant stand against anti-government demonstrations but on Monday said he was willing to meet with some of the leaders of the dissent.