File photo: CGTN

Two large and shallow earthquakes struck off Indonesia's Sumatra island early Wednesday, the US Geological Survey reported, but no tsunami warning was issued.

The quakes, of magnitude 6.8 and 6.9, struck within six minutes of one another from 5:23 am (22:23 GMT Tuesday). 

The Indian Ocean Tsunami Warning and Mitigation System said there was "no threat to countries in the Indian Ocean".

There was a "low likelihood of casualties and damage", the USGS added.

The Southeast Asian archipelago experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire", where tectonic plates collide.