TORONTO - Toronto Mayor David Miller said the U.S state department's travel advisory for Toronto is unnecessary.

The department issued the advisory because of the G20 summit, citing concern over the potential for large-scale demonstrations leading up to and during the weekend event.

The alert warns U.S. citizens living in or travelling to Toronto to avoid protests and demonstrations during the G20.

"Even demonstrations that are meant to be peaceful can become violent and unpredictable," the alert warns.

It also recommends Americans avoid travelling in or through downtown Toronto during the summit, if possible.

"While I respect the state department's right to do what it thinks is in the best interests of U.S. citizens, I feel this alert is an overreaction," Miller said in a statement.

"It is true that parts of downtown Toronto, the roads in and around the security zone and highways leading into and out of the city will see disruptions at varying times. But there are many other parts of downtown Toronto that will remain unaffected by the summit."

Toronto universities, theatres, banks and galleries have announced they will close when leaders of the world's G20 countries converge in Toronto for their summit on June 26 and 27.

In anticipation of protests and demonstrations, security officials have constructed a fence around the Metro Toronto Convention Centre, where leaders will be meeting. Security during the summit is expected to be tight.

"I would encourage everyone, whether they be citizens of the U.S., Canada, or any other country living in or visiting Toronto to experience the many outstanding attractions, excellent restaurants or vibrant neighbourhoods that populate our great city," said Miller.

The state department's travel alert expires June 28.