The US Geological Survey said the first quake had a magnitude of 6.4 and a depth of 11 kilometres, striking 109 kilometers northeast of Tonga's Hihifo district Monday night.
It was followed 30 minutes later by a magnitude-6.5 quake that had a depth of 15 kilometres and struck 99 kilometres northeast of Hihifo.
Leveni Aho, Director of Tonga's National Emergency Management Office, said his staff was trying to make contact with officials on the islands near the epicenter, but had not received any reports of damage.
"I think if there was anything significant, it would have been reported by now," Aho said.
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In Samoa, the quakes were felt throughout most of the islands, and lasted less than a minute, said Filomena Nelson, assistant chief executive officer of the nation's Disaster Management Office.
There were no reports of damage, she said.
The Hawaii-based Pacific Tsunami Warning Center said there was no threat of a tsunami.
Earlier today, a powerful quake rattled the South Pacific nation of Papua New Guinea, generating a small tsunami but prompting no reports of injuries or damage.