A strong 6.4-magnitude quake struck off the Indonesian island of Sumatra on Saturday, the US Geological Survey said, but no tsunami warning was issued.

The quake struck at a shallow depth of just 23 kilometres (14 miles), off the west coast of the vast island and 154 kilometres southwest of Sungaipenuh, said the USGS.

Suharjono, an official from the local meteorology, climatology and geophysics agency who goes by one name, said there was no threat of a tsunami.

The quake came just days after a strong inland tremor in Aceh province, on the northern tip of Sumatra, that killed dozens of people and left thousands homeless.

Indonesia sits on the Pacific "Ring of Fire" where tectonic plates collide, causing frequent seismic and volcanic activity. (AFP)