By Allison Lampert and Nia Williams

MONTREAL/CALGARY (Reuters) - Canada's National Energy Board canceled the first day of hearings on TransCanada Corp's <TRP.TO> proposed Energy East pipeline in Montreal on Monday after protesters disrupted the panel session, an agency spokeswoman said.

Montreal police said three protesters were arrested on obstruction charges, with two of the three also charged with assaulting a police officer.

Footage posted on Twitter by local media showed protesters at the downtown venue standing, clapping and chanting at the panel.

Environmental groups opposed to Canadian oil sands development have fought the 1.1 million-barrel-per-day Energy East pipeline, which would carry crude oil from Alberta to Canada's Atlantic coast.

Opposition has been particularly strong in the French-speaking province of Quebec, which the pipeline would need to cross on its way to the coast. Opponents include Montreal Mayor Denis Coderre, who has cited concerns the route could endanger forest and agricultural land.

Coderre told reporters on Monday that the public needs answers on the number of jobs that will be created from the pipeline and TransCanada's contingency plan in case of a spill.

"There are 4 million people here," he said of the Montreal area. "Can we afford to take a chance?"

Unionized workers hoping to benefit from the construction work estimate the pipeline would create 2,000 jobs over three years in Quebec, a province where private investment in large projects has been hit by weak commodity prices.

"Until 2014 there was a shortage of workers," said construction union representative Eric Verdon, while gathered with unemployed members to protest in favor of Energy East. "Now they can't find jobs."

There is no word yet on a new date for the hearing, said NEB spokeswoman Sarah Kiley.

"We are standing by and ready to respectfully and constructively begin the sessions in Montreal after five such productive sessions in New Brunswick – and we will be ready when the sessions resume," TransCanada said in a statement.

Calgary-based TransCanada also proposed building the controversial Keystone XL pipeline, which was denied a U.S. presidential permit by Barack Obama last year, and is a frequent target of environmental protesters.

Energy East has had several setbacks in Quebec. In March, the provincial government filed an injunction against the pipeline to force an environmental review, which TransCanada later agreed to.

Last November TransCanada scrapped plans to build a marine crude oil export terminal in Quebec.

(Editing by Marguerita Choy and Bill Trott)