The warnings caused thousands of residents to flee to higher ground in at least two Pacific islands.
The Pacific Tsunami Warning Center said sea-level readings indicated a tiny tsunami formed after a quake with a magnitude of 7.8 struck 183 miles (294 kilometers) northwest of the Vanuatu island of Santo, and 354 miles (596 kilometers) northwest of the capital of Port Vila, at a depth of 21 miles (35 kilometers).
Just 15 minutes later a second quake with a magnitude of 7.3 hit at the same depth but 21 miles (35 kilometers) farther north of Santo and Port Vila. A third of magnitude 7.1 was recorded nearly an hour later, 175 miles (280 kilometers) northwest of Santo at a depth of nine miles (15 kilometers).
The Hawaii-based warning center immediately issued a regional tsunami warning for 11 nations and territories and a lower-level tsunami watch as far away as Australia and Hawaii. The center canceled all warnings two hours later.
There were no immediate reports of injury or damage from officials in Vanuatu, a chain of 83 islands. It lies just over 1,400 miles (2,200 kilometers) northeast of Sydney, Australia.
"We have no damage reports yet, but we have had no contact with Santo so far," Vanuatu police spokesman Take Rakau told The Associated Press.
While the quakes were not felt in Port Vila, he said Santo, with its capital of Luganville, "most likely could have felt them."
"The (nation's) National Disaster Management Office has sent out a tsunami warning," he added.
In Tuvalu, a low-lying nation of eight coral atolls with about 10,000 people, thousands fled inland, some clustering around the government building in the capital, Funafuti - the only multistory building in the country.
"We've had a bulletin canceling the warning, and that has been broadcast," weather office head Hilia Vavae told The AP. "Even though nothing happened, it was a good exercise for us. We now can react and get to safety."
The latest warning comes just 10 days after a quake of magnitude 8.3 rocked the South Pacific near Samoa, sparking tsunami waves that killed at least 178 people and devastated coastal villages in Samoa, American Samoa and in northern Tonga.
The alerts Thursday created worry in American Samoa, where at least 32 people were killed and hundreds of homes destroyed in the Sept. 29 tsunami. Residents of the coastal village of Utulei fled to the hills after hearing there was a tsunami watch for the U.S. territory.
Schools, government building and other residents were also evacuated to higher ground. Traffic was snarled in downtown villages of Pago Pago and Fagatogo.
Also Thursday morning, the U.S. Geological Survey reported a strong earthquake struck south of the Philippines.
The quake had a preliminary magnitude of 6.7 and was located in the Celebes Sea, 175 miles (282 kilometers) southeast of Jolo, Sulu Archipelago, and 730 miles (1,175 kilometers) south of Manila. The quake hit at 5:41 a.m. Thursday local time.
USGS did not report any damages or injuries.
Associated Press writers Kristen Gelineau in Sydney and Jaymes Song in Honolulu, Hawaii, contributed to this report.