LAVAL, Que. -- Gilles Vaillancourt, once one of Quebec's most influential municipal politicians, was sent to prison Thursday for his role in a scheme that defrauded public coffers of millions of dollars.

The former longtime mayor of Laval, Quebec's third-largest municipality, pleaded guilty to three charges -- conspiracy, fraud and breach of trust -- and was incarcerated after defence and Crown lawyers agreed to a six-year prison term.

Under a joint Crown-defence agreement, Vaillancourt, 75, must reimburse about $7 million, mostly from Swiss bank accounts, as well as hand over his $1-million condominium to the city he headed for 23 years.

Crown prosecutor Richard Rougeau estimated the fraud totalled several dozen million dollars between 1996 and 2010.

"I sincerely regret the errors I made and the grief I have caused my family, my friends and especially the citizens of Laval," Vaillancourt told Quebec Superior Court Justice James Brunton.

"I feel great pain and I know this pain will stay with me, maybe until the end of my days. I offer my sincere apologies. I did great things in Laval but the errors I made are not acceptable. I understand that. I hope to serve my sentence as quickly as possible and try to become an asset to society once again."

About $1.7 million has already been given to Quebec authorities, while another $5.23 million is currently being transferred from Swiss bank accounts.

The City of Laval has taken possession of his $1-million condominium as well as a sum of $300,000. Vaillancourt will also be deprived of $300,000 in pension payments.

The judge is expected to rule in two weeks on the Crown-defence recommendation.

"We are confident the court on Dec. 15 will endorse the agreement reached by the various parties," Rougeau said.

Vaillancourt was Laval mayor between 1989-2012 and earned the nickname, "The Monarch," throughout his 23-year reign.

He was accused of taking part in a scheme whereby the City of Laval doled out municipal contracts in exchange for bribes and illegal donations from construction entrepreneurs.

Vaillancourt was among 37 people originally arrested in May 2013 by Quebec's anti-corruption unit.

He faced a dozen charges including conspiracy, fraud and corruption-related counts as well being one of three accused on the more serious charge of gangsterism.

The arrest came just months after the cloud of suspicion forced Vaillancourt to quit politics in November 2012.

In the weeks leading up to the mass arrests, police had raided numerous engineering firms and businesses in addition to Vaillancourt's own home, condo, offices and his bank safety deposit boxes.

Thursday's proceedings began with Brunton asking Vaillancourt whether he had intended to commit the crimes to which he pleaded guilty.

Vaillancourt answered he did not have that intention, prompting Brunton to temporarily suspend proceedings. When they resumed, Vaillancourt said he had planned to commit the crimes.