A major 7.8-magnitude quake has hit Indonesia's northern Sumatra, US seismologists say, triggering a local tsunami watch.
The quake struck at a depth of 46 kilometres, just off northern Sumatra, at 5:15am on Wednesday (0815 AEST), according to the US Geological Survey (USGS).
The Pacific Tsunami Warning Center issued a watch for local tsunamis but said a widespread destructive tsunami was not expected.