Any protester who refuses to leave will be arrested, police said. There have been reports of injuries and of pepper spray being used by officers.

Around 200 Occupy Wall Street protesters have been staying in Zuccotti Park overnight and, as police moved in to remove them and pull down tents, demonstrators gathered, linking arms and chanting, “Whose park? Our park!” and “This is what a police state looks like.”

In the centre of the park, barricades were hastily made from furniture and pieces of wood.

Earlier on Tuesday, City Mayor Michael Bloomberg tweeted: “Occupants of Zuccotti should temporarily leave and remove tents and tarps. Protesters can return after the park is cleared.”

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Police spokesman Paul Browne said the city and the owners of the park issued fliers to the protesters saying the park would be cleared for cleaning shortly after 1am on Tuesday.

A message on the flier said that: “That the continued occupation of Zuccotti Park posed an increasing health and safety hazard to those camped in the park, the city’s first responders and the surrounding community.”

The Occupy Wall Street protest has been encamped in Zuccotti Park since September 17. On it’s website, the group says: “We Are The 99% that will no longer tolerate the greed and corruption of the 1%. We are using the revolutionary Arab Spring tactic to achieve our ends and encourage the use of nonviolence to maximize the safety of all participants.”

As the police continue to remove tents and protesters, the group promised: “We will reoccupy.”