Police said that a number of youths broke into the disused former headquarters of the Bank of Ireland on the city's main thoroughfare, Royal Avenue, the daily The Guardian reported.
They said that about a dozen protesters, some of whom were masked, remained inside the building at the corner of North Street and Royal Avenue.
Some of the demonstrators had occupied the top floor and draped anti-capitalist banners over the exterior, the report said.
A police helicopter hovered over the former bank but did not initially attempt to make any arrests.
Bank of Ireland is one of the Irish banks rescued from collapse by billions of euros from the Republic's taxpayers.
The Royal Avenue branch near to the Belfast Telegraph newspaper has been closed for several years.
"Occupy Belfast have taken control of the Bank of Ireland on Royal Avenue in opposition to soaring homelessness, lack of affordable social housing and home repossessions", said a statement from the anti-capitalist demonstrators.
Stating that they hoped for the "building of a housing campaign", the protesters added: "Banks take our houses so we take their buildings. This is a repossession for the community!"
Occupy protests have been held across the world, with the most high-profile demonstrations taking place outside Wall Street in New York and St. Paul's Cathedral in London.
In Belfast a small band of Occupy activists have been camped out for the last few months on Writer's Square facing onto St Anne's Cathedral in Donegall Street.