FLORENCE, Nov 9 (Reuters) - Italian gas grid operator Snam will start work on a new LNG terminal in Piombino soon, the mayor of the Tuscan city said on Wednesday, adding that the local administration was working on a legal complaint against the project.

A source close to Snam said that the group had communicated to local entities that it would start the procedures soon that are needed to build the pipeline connecting the LNG terminal to the grid. By end-November the construction works will begin, they added.

The terminal needs to be operational by end-March to help Italy replace dwindling gas supplies, Claudio Descalzi, CEO of energy group Eni, said, adding the timely completion of the project was crucial to re-fill the country's gas storages by the next winter. Eni will use the terminal to import LNG.

Piombino's mayor Francesco Ferrari said on Wednesday he would also put pressure on Snam to deliver compensation in exchange for allowing the energy infrastructure to be built.

He is leading a local protest against the project, which highlights risks to safety, environment and local businesses, including fish-farming.

The region of Tuscany has asked for more than 450 million euros in investments in exchange for allowing the new floating storage and regasification unit (FSRU) in the Tuscan port, the Italian region said last month. (Reporting by Silvia Ognibene; writing by Francesca Landini, editing by Jane Merriman)