TORONTO - The G20 summit appears destined to inflict a blinding migraine on Canada's largest city, even if protests prove peaceful.

Motorists, cyclists, pedestrians, commuters, businesses, condo residents, travellers, sports fans -- even tipplers -- will all feel at least some pain as next month's summit invades the downtown core.

Security for world leaders, delegates and observers, already estimated at more than $1 billion for both the G8 and G20 summits, entails turning a swath of some of the country's busiest real estate into all but a no-go zone.

"It's not about shutting the city down," Toronto police Supt. Tom Russell said Friday.

"Every effort is being made to ensure these security measures have the least possible impact on the day-to-day lives of Torontonians while balancing the need to keep some of the world's most powerful people safe and secure."

Ground zero for the June 26-27 summit is the cavernous Metro Toronto Convention Centre, located on busy Front Street across the road from the CBC headquarters, and nearby hotels.

Access to the highest-security zone around the centre -- which remains subject to change -- will be controlled by a perimeter fence that spans several blocks. Included in the zone are such landmarks as the CN Tower, which will be closed.

Union Station, just outside the zone, will remain open although pedestrian traffic will be strictly funnelled.

"It's a huge operation," said RCMP Chief Supt. Phonse MacNeil, head of the Integrated Security Unit.

Residents and workers within the zone will face police checkpoints and hassles trying to reach their destinations, even with registration and accreditation.

More than 20,000 people have received accreditation to date, but thousands more have yet to apply.

Police have asked parents to keep their children out of area daycare centres and some downtown patios will be forced to close.

Toronto Coun. Adam Vaughan, whose ward will be heavily impacted by the summit, lambasted Prime Minister Stephen Harper for leaving businesses to fend for themselves.

"Stephen Harper has an obligation to Canadian taxpayers: If he can spend $1 billion protecting his photo-op, he can spend money protecting the businesses and the residences," he said.

"He's going to spend more on haircuts for this thing than we're going to get in compensation. I don't know how you justify that."

Construction of the fence is set to start June 7 and continue round the clock until it's completed.

The area will be closed off completely on the evening of Friday June 25, the eve of the weekend summit. An unspecified number of gates will allow tightly controlled access during the summit.

Anyone wishing to enter the secure zone will have to present photo identification and "clearly articulate" a specific purpose and destination to be allowed through.

"We know this will be inconvenient," Russell said. "We ask for your patience and understanding."

Along with the security fence, a massive uniformed police presence -- bolstered by private guards -- will be the visible face of the security presence aimed at deterring any terrorist attacks or violence by demonstrators protesting G20 countries' human-rights and environmental records.

Details of the security measures came 10 days after anarchists claimed responsibility for firebombing a bank in Ottawa, and just hours after anti-G20 slogans were spray-painted overnight at several downtown Toronto banks and ATMs.

One man faces mischief charges in connection with the graffiti, which included slogans such as "Stop G20" and "Resist G20."

Authorities have said air travellers through Toronto could face some delays as G20 leaders come and go.

Police also said Friday traffic will be diverted around the security zone, causing "significant" disruption for motorists who normally use some of the key east-west and north-south routes through the area.

The broader traffic zone stretches to Spadina Avenue in the west, Yonge Street in the east, King Street to the north and Queens Quay Boulevard in the south. Police warn that area, which encompasses the Hockey Hall of Fame, the Rogers Centre, and the Air Canada Centre, will see significant disruptions.

Key highways -- Highway 427 and the Gardner Expressway -- will be severely impacted as dozens of motorcades make their way to and from the airport.

GO Transit, whose commuter train routes run just south of the convention centre, is taking unspecified security measures.

The city's subway system is expected to function normally, spokesman Brad Ross said.

"The challenge we'll have is if there are protests or demonstrations that affect any of our surface routes," Ross said.