* 7.7 magnitude undersea earthquake strikes South Pacific region
* No immediate reports of damage near epicentre in New Caledonia (Adds French govt and Vale statements)
By Praveen Menon and Renju Jose
WELLINGTON/SYDNEY, Feb 11 (Reuters) - A powerful 7.7 magnitude undersea earthquake struck the South Pacific on Thursday, triggering tsunami warnings in the region that were later cancelled, with no immediate reports of damage.
The European Mediterranean Seismological Centre (EMSC) said the quake's epicentre was 417 km (258 miles) east of Tadine, a town in the French territory of New Caledonia, and at a depth of 10 km (6.2 miles).
France's ministry for overseas territories said in a tweet on Thursday there were no immediate reports of damage or casualties in New Caledonia.
A spokeswoman for Vale SA's nickel business in the French territory said there was no damage to facilities. Vale's nickel operations have been halted since December due to large-scale protests linked to the proposed sale of its local assets.
Tsunami centres across the region sent alerts for the public to stay off beaches due to risks of unexpected currents and unusual waves shortly after the earthquake.
The U.S. Tsunami Warning System later said the tsunami threat had passed for the region, although warned there may be minor sea fluctuations.
The quake followed at least three other tremors in the region with magnitudes ranging from 5.7 to 6.1 in a span of just over an hour. Large tremors were also recorded after the 7.7 magnitude shock.
There were no immediate reports of damage near the epicentre in New Caledonia, John Ristau, a seismologist from New Zealand-based GNS Science, told NewsHub's The AM Show.
"It's most likely that damage would have been minimal if anything at all," he said, adding that Thursday morning's earthquake could trigger more tremors. (Reporting by Praveen Menon and Renju Jose; Additional reporting by Sonali Paul and Bhargav Acharya; Writing by Jonathan Barrett; Editing by Toby Chopra, Rosalba O'Brien and Lincoln Feast.)
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