SYDNEY (AP) — A pair of strong earthquakes struck off the South Pacific nations of Tonga and Samoa on Monday, but there were no immediate reports of injuries or damage and no tsunami warning was issued.

The U.S. Geological Survey said the first quake had a magnitude of 6.4 and a depth of 11 kilometers (7 miles), striking 109 kilometers (68 miles) 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 kilometers (9 miles) and struck 99 kilometers (62 miles) 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. No tremors were felt on Tonga's main island, located about 600 kilometers (370 miles) south of Hihifo, he said.

"I think if there was anything significant, it would have been reported by now," Aho said.

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 Monday, a powerful quake rattled the South Pacific nation of Papua New Guinea, generating a small tsunami but prompting no reports of injuries or damage.

Earthquakes are common in the region, which lies on the "Ring of Fire" — an arc of earthquake and volcanic activity that stretches around the Pacific Rim.