More than 500,000 revellers are expected to flock to Parliament Hill Saturday to celebrate Canada’s 150th anniversary, and heightened security will be in place across the capital to ensure the party goes off without a hitch.

Heavily armed police and surveillance cameras will be strategically placed throughout the event, and a barricade will be positioned around the party to thwart any attempted attacks by vehicles.

The security measures, which one source described as “unprecedented,” come as a national security memo obtained by CTV News warns that ISIS “explicitly named Canada” and the United States as potential targets after the Manchester attack in May.

According to the memo, ISIS has warned Muslims to avoid markets and public gatherings in Canada, and threatened to use “explosives, vehicles and beheadings to kill crusaders.”

“Given the current threat environment it is increasingly necessary for law enforcement officers to be aware of possible suspicious incidents that may be indicative of pre-attack planning,” the memo says. “ The planning cycle of self-directed extremists is becoming increasingly shorter and subsequently more difficult to attack.”

Sources say there are no specific or credible Canada Day plots on the radar. Canada’s terror threat remains at medium, meaning that a violent act of terrorism could occur. The level has remained at medium since October 2014.

Officials aren’t taking any chances when it comes to safety precautions. The increased safety measures in Ottawa will mean that every available police officer will be on duty Saturday.

“The events that are happening globally are informing us how we’re going to be adjusting our security posture,” Mike O’Beirne, acting director of the Parliamentary Protective Services, told CTV News.

Ottawa Police Service spokesman Chuck Benoit says the public should not be alarmed to see officers visibly armed.

“You're going to see officers with carbines and long guns in the area. It's not to scare anybody but it's a precaution we have to have in measure,” Benoit said.

Streets surrounding Parliament will be shut down days earlier than usual to start the safety preparations. Police will shut down a larger area for the celebration than in previous years to accommodate the massive influx of people expected to attend the party.

Concrete blocks and dump trucks will be installed around the party to stop any attempted attacks by vehicles.

“More likely than not, somebody who is going to try this low tech approach, has never been in anybody's database,” said former CSIS director Richard Fadden.

Sources say that, behind the scenes, the national security community has been working diligently to identify any possible threats to the Canada 150 celebrations and thwart them before Saturday.

Boosted security measures have been extended to cities across the country, which are similarly ramping up road closures and bolstering police presence at the celebrations.

With a report from CTV’s Mercedes Stephenson in Ottawa