Santiago: An earthquake of magnitude 6.9 has struck off the coast of Chile, rocking the capital Santiago and generating at least two significant aftershocks.

The United States Geological Service reviewed the initial magnitude down from 7.1.

The quake struck 35 kilometres west of the popular holiday city of Valparaiso. Credit:USGS

No major damage was immediately apparent, according to an assessment by Chile's emergency services. The Chilean Navy and the Pacific Tsunami Warning Centre said the quake was not expected to cause a tsunami.

Chile's state-run Codelco, one of the largest copper mining companies in the world, said its operations were unaffected.