At least 21 people have been killed and more than 300 people are injured after the most powerful earthquake to hit Albania in decades rocked the capital and surrounding region, causing several buildings to collapse and bury residents in the rubble.

Residents, some carrying babies, fled apartment buildings in Tirana and the western port of Durres after the 6.4 magnitude quake struck shortly before 4am local time.

The US Geological Survey reported that the earthquake was centred 30 kilometres west of the capital, Tirana, at a shallow depth of 10km, and was the second powerful tremor to hit the region in two months.