A tsunami generated by a powerful earthquake in Canada hit the US state of Hawaii late Saturday, an official from the Pacific Tsunami Warning Center said.

"The tsunami is arriving right now," Gerard Fryer, a senior geophysicist with the center, told reporters. "It is coming in as we speak."

Television images from the island of Oahu showed relatively small waves peacefully rolling toward the shore.

But Fryer urged Hawaii residents not to deceived by appearances.

"Typically, the first wave is not the largest," he said, adding that subsequent waves could be much larger, resulting in flooding in low-lying areas.

"If the waves are big, the all-clear may take six or seven hours," Fryer said.