SENDAI, Japan, May 20 (Reuters) - Participants of an informal symposium with Group of Seven finance leaders and academics on Friday agreed a so-called "Brexit" vote for Britain to exit the European Union at a referendum next month could lead to financial market unrest, a G7 source said.

Participants of the symposium, which is closed to the media, also agreed that relying on monetary policy alone would not lead to sustainable growth, the source said.

There were no demands for quick economic stimulus programmes, the source said, adding that there was instead a wide recognition among the participants that structural reforms combined with appropriate investment would strengthen growth.

The G7 finance ministers and central bank governors are gathering in Sendai, northeastern Japan, for discussions on the global economy and its risks.

Ahead of their first-day session kicking off on Friday, they met with prominent academics, including Nobel Prize-winning economist Robert Shiller, for informal talks on ways to boost the global economy.

(Reporting by Gernot Heller and Leika Kihara; Editing by Chris Gallagher)