A group of protesters gathered outside Citi's headquarters in New York chanting "break big banks."

Made up largely of Senator Elizabeth Warren's supporters, the protesters on Thursday specifically targeted Citigroup (C) because of the bank's role in watering down Wall Street regulation.

"We need to break up the big banks that have too much power in our democracy," said TJ Helmstetter, one of the protest organizers. "They literally wrote the law and Washington let them do it."

Warren, a Massachusetts Democrat, has blasted her fellow lawmakers for passing legislation that undoes a central piece of the Dodd-Frank financial reform law.

"I believe banks have too much concentrated power in our democracy and we want it back," said Emmett Grant, pictured below, a 52 year-old from Mount Vernon, NY.

Protesters carried signs that read "#StandWithWarren" on a chilly morning outside Citigroup's Park Avenue tower with about a dozen police officers standing by.

Organizers called for a modern day Glass-Stegall Act, the 1933 legislation that separated the money lending banks from investment banks. They claimed to have 15,000 signatures on a petition calling for this sort of law to be reinstated.

"I'm here to support breaking up big banks," said Marni Halasa, a New York-based performance artist, pictured below.

The group of about 20 protesters also took aim at President Obama's nomination of Antonio Weiss, an investment banker, to a key Treasury Department post.

Warren has been a vocal opponent of Weiss's nomination for the position that oversees domestic banks and financial regulations.

From Citigroup, the protesters walked a few blocks south to the New York offices of Lazard, where Weiss works as a senior deal maker.

This may be the first time protesters have taken to the streets over the nomination of a Treasury undersecretary.

Critics say Weiss was involved in a deal to help Burger King avoid paying taxes by merging with a Canadian company. He also stands to walk away with a $20 million "golden parachute," they said.

"We know where his loyalties lie. Not with us. He's with the big money people," said Skip Roseboro, an organizer with New York Communities for Change.

It's not unusual for investment bankers to go to work in the public sector. But the protesters objected to this "revolving door" between Washington and Wall Street.

"America should be a land of opportunity for everyone, not just people who work at banks," said Tim Wu, a Columbia law professor, who also took part in the protest.