Demonstrators broke into an office building used by mining company Xstrata in central London Wednesday and hung protest banners on the roof before police regained control of the building.

A group of about 60 from the Occupy movement entered the offices in Haymarket in protest at the pay of the company's chief executive, Occupy said in a statement.

Led by a samba band, they chanted and unfurled a banner which said: All power to the 99 percent.

A spokeswoman for Xstrata said in a statement: All executive pay is approved by the company's shareholders and is linked to company and individual performance.

Police removed the demonstrators and threw a cordon along the Haymarket, effectively sealing off the immediate area.

At approximately 1550 hours (GMT) a containment was put in place outside Panton House, Haymarket, to prevent disorder by a group of protesters outside the building, police said in a statement.

Some protesters have entered the building and officers are in the process of making arrests for aggravated trespass.

It was unclear how many people were arrested.

TV footage showed demonstrators walking up and down the staircase, watched by members of staff.

The raid took place on the same day as thousands of public sector workers marched through London as part of a national day of protest against government plans to change their pensions.

In this time when the government enforces austerity on the 99 percent, these executives are profiting, Karen Lincoln of Occupy London said in a statement.

Occupy London grabbed the headlines last month when they pitched about 200 tents outside St Paul's Cathedral after they were thwarted in an attempt to stage a protest outside their initial target, the London Stock Exchange.

Their protest is part of a global movement for social and economic change. They say economic and political power lies in the hands of just 1 percent of the population.

(Reporting by Avril Ormsby and Clara Ferreira Marques)