A strong earthquake shook Ottawa and Montreal in eastern Canada today, forcing office workers out onto downtown streets in the nation's capital.

The US Geological Survey reported the temblor of a magnitude of 5.5 hit the Ontario-Quebec border area at 1741 GMT, rattling downtown Ottawa shortly after midday.

The USGS said the epicenter was 61 kilometers (38 miles) north of Ottawa.

AFP journalists witnessed walls in downtown office buildings shook for several seconds. Cracks appeared in the Parliamentary Press Gallery building in Ottawa, and outside. Some people appeared shaken up, but unhurt.

Most downtown Ottawa buildings appeared to have been evacuated as alarms rang out.

James Bowden, a former resident of Alaska who experienced several earthquakes in the US state, was standing in line at a fast-food restaurant on Ottawa's Sparks Street when he said he "heard the earthquake coming a few seconds before it hit."

"It sounded like a freight train barreling towards us," he said.

An avid reader of earthquake sciences, Bowden said Ottawa experiences earthquakes every four or five years. "This one was fairly big," he said.

"It was really... freaky," a pedestrian was overheard saying on her cell phone as she walked by.