GUELPH, Ont. - Prime Minister Stephen Harper is extending Canada's "heartfelt condolences" and a helping hand to the people of quake-stricken Japan.

Harper spoke Friday with Japan's ambassador to Canada to say the country's thoughts and prayers are with his people after a powerful earthquake that triggered a devastating tsunami.

"I offered any support and assistance that may be needed by that country," Harper told a news conference in Guelph, Ont.

"Our officials at the Canadian embassy in Tokyo are working with Japanese authorities to determine whether any Canadians have been injured by the earthquake or the tsunami."

Harper also acknowledged the potential risk of the tsunami's waves reaching Canada's west coast; residents of Vancouver Island spent the morning under a tsunami advisory as they kept a wary eye on the shoreline.

Although the advisory was still in place, it appeared as if the worst had already passed, Harper said.

"My understanding is there are good emergency plans in place, particularly in that part of the country for this particular type of event," he said.

"I'm told by people who have lived on the west coast that there are tsunami plans and there are regularly exercises to test those out. It does look as if the worst has passed."

Authorities are on notice and prepared to deal with any emergencies, he added.

Ontario Premier Dalton McGuinty was also among those political leaders who extended their sympathies to the families of the victims.

"We have strong ties with Japan and its people," McGuinty said in a statement.

"When a natural disaster happens on the other side of the world, our global ties remind us of how connected we are."

The 8.9 magnitude temblor, one of the worst in modern history, erupted off the northeastern coast of Japan near the city of Sendai, promptly unleashing a seven-metre tsunami that left a swath of devastation deep inside the island nation's eastern shoreline.

Meanwhile, U.S. President Barack Obama says the earthquake and tsunami in Japan are a potentially "catastrophic" disaster, and he says his thoughts and prayers are with the Japanese people.

Speaking at a White House news conference, Obama says the U.S. is prepared to send whatever assistance Japan requests. He says one aircraft carrier is already in Japan and another is on its way.

Tsunami waves have also swamped Hawaii beaches and grazed the West Coast. Obama says that his administration is monitoring the impact of the tsunami on the U.S. closely.

With files from The Associated Press