A 6.8-magnitude earthquake struck in the South Pacific off the coast of the Polynesian kingdom of Tonga, sending panicked residents in many of the country's islands into the streets at night, but there were no immediate reports of damage or injuries.

Shortly after the quake struck at 1:47 a.m. local time Wednesday (7:47 a.m. ET Tuesday), the U.S. government's Pacific Tsunami Warning Center in Hawaii reported that there was no threat of a destructive widespread tsunami, although waves were possible within 100 kilometres of the epicentre.

"There's no indication of damage right now in this area," said Faleo Vico, a weather office staff person in the Tongan capital, Nuku'alofa, 195 kilometres southwest of the epicentre.

Residents in Nuku'alofa said their homes rattled and the tremors set off frantic barking of dogs.

In the town of Ha'apai, on an island 300 kilometres northeast of the capital, resident Lano Fonua said the quake was strong and lasted about 45 seconds.

"Many people went out into the streets as the quake was shaking the area quite a bit. It was really going," he said. "We don't have any reports of major damage here in the centre of town."

The U.S. Geological Survey said the quake measured 6.8 in magnitude and was localized at a depth of 62 kilometres under the ocean.

On Sept. 29, a tsunami spawned by a magnitude-8.3 earthquake killed 34 people in American Samoa, 183 in Samoa and nine in Tonga.