A strong 6.6-magnitude earthquake struck off northwest Australia Sunday, shaking buildings over a wide area but causing no immediate reports of damage or injuries.

The shallow quake hit early Sunday afternoon 10 kilometres under the Indian Ocean 203 kilometres (126 miles) west of the West Australian beach resort of Broome, the US Geological Survey said. No tsunami alert was issued.

Sergeant Neil Gordon of the Broome police department said the quake rattled the city for more than a minute.

"The building here was shaking for about a minute and a half ... a steady shaking for that period of time," he told AFP by telephone.

He added that there had been "no reports of any injuries or any damage throughout the district," following the tremor.

The national broadcaster ABC said there were some reports of minor damage from the quake, and no injuries.

Australian media said the tremor was felt across a long stretch of the northwestern coast of Australia, from the West Australian capital of Perth and the mining centres of Karatha and Port Hedland to the south and as far as Darwin to the north.