Thick concrete blocks and steel poles holding wire-mesh fencing have gone up overnight just south of the Rogers Centre as crews start installing security barriers for the G20 summit.

The nearly three-metre-high fence stretches along Rees St. from Lake Shore Blvd. W. to Bremner Blvd., with another barricade stretching about 20 metres along Lake Shore south of the Steam Whistle Brewery.

Barricades were also stacked up between the CN Tower and Rogers Centre.

Frames for the fencing have been installed on Bremner, south of the CN Tower.

Security fences will go up in two phases. The outer or yellow zone, is a pedestrian- and traffic-controlled area around the Metro Toronto Convention Centre, Union Station and the Rogers Centre.

The innermost security zone, the red zone, will wrap around the convention centre and other nearby buildings.

Officials said multiple gates with security checkpoints will eventually be erected but plan to keep the area open to vehicles and pedestrians up until the evening of June 25. The G20 summit runs June 26-27.

Residents and workers who need access to the yellow zone can ask for a registration card, which will require submitting photo ID and personal information to the summit office.

During the summit weekend, the red zone will be sealed by a three-metre fence and five levels of security screening.

With files from Alex Hering