BEIJING, China -- Two people were killed and dozens injured when a shallow earthquake struck southwestern China in the early hours of Thursday, triggering the second-highest level of emergency response by rescuers in Sichuan province, state media said.

The US Geological Survey put the magnitude of the quake at 5.4 but the China Earthquake Networks Centre measured it at magnitude 6.0. Both put it at a shallow depth of 10 kilometres (six miles).

It struck Luxian county around 120 kilometres southwest of the sprawling megacity of Chongqing, which along with its surrounding area is home to around 30 million people.

Luxian authorities said the seismic event had left "two dead, three seriously injured and 50 slightly injured, while 22 houses in the county collapsed".

Scores of houses have been damaged, while communications had been disrupted in parts of the county.

China Global Television Network (CGTN) confirmed the death toll, while other media shared images of buildings with large cracks caused by the quake.

The Xinhua news agency said Luzhou City had sent emergency personnel to the area, without elaborating.

USGS said that "significant damage is likely and the disaster is potentially widespread", in a preliminary assessment.

A powerful 7.9-magnitude quake in Sichuan province in 2008 left 87,000 people dead or missing.

Among them were thousands of children, killed when poorly constructed school buildings collapsed, but the government failed to release an exact number of dead as the issue took on a political dimension.