Magnitude 6.9 earthquake has struck south of Fiji in the Pacific Ocean.

A tsunami threat message was issued by the Pacific Tsunami Warning Centre after the quake hit at 11.52am local time (9.52pm GMT).

"Hazardous tsunami waves from this earthquake are possible within 300km of the epicentre along the coasts of Fiji," it said.

The warning centre later lifted the alert, saying the threat "had passed" while urging people to remain vigilant for minor fluctuations in sea level that could occur.

When the tsunami alert was issued, workers in the Fijian capital fled their offices and headed inland for safety, but had returned by early afternoon after authorities confirmed it was safe. 

The earthquake's epicentre was measured at almost 11 miles (17km) deep along the boundary between the Australia and Pacific continental plates, the US Geological Survey said.

Fiji's Principal Disaster Management Officer, Sunia Ratulevu, said there had been no reports of damage or injuries from the quake, and no unusual wave activity had been reported. The quake struck far offshore and was not felt in the cities of Suva or Nadi, he said. 

It was followed by at least seven major aftershocks of of magnitudes between 4.9 and 5.8, the USGS said.

Fiji lies within the "Ring of Fire", a seismically active region that seas frequent earthquakes and volcanic eruptions because of the shifting tectonic plates beneath.

A 2004 quake and tsunami killed a total of 230,000 people in a dozen countries, most of them in Aceh, Indonesia. 

(Independent)