A massive magnitude 7.8 earthquake rocked the South Pacific island nation of Tonga on Thursday, triggering international warnings of a potentially lethal tsunami — but those messages failed to reach the tiny nation.

The warning raised jitters from Hawaii to New Zealand, until authorities called it off two hours later because the quake never generated any massive waves. The 4:26 a.m. earthquake, about 150 kilometers (95 miles) south of the Tongan island of Neiafu, did little damage to South Pacific countries beyond breaking windows.

However, the tsunami warnings did not reach Tonga, raising troubling questions about the effectiveness of such alerts, which have come under global scrutiny since an earthquake-driven tsunami in the Indian Ocean nearly 18 months ago left at least 216,000 people dead or missing in a dozen countries.

Mali'u Takai, deputy director of Tonga's National Disaster Office, told The Associated Press in a telephone interview that the system that should have passed on an alert from the Pacific Tsunami Warning Center in Hawaii had malfunctioned.

"Nobody got a warning through the emergency satellite system in our meteorological office," Takai said. "Judging by the location of the epicenter we would have been caught out without any warning at all because of the systems malfunction." He did not elaborate.

Andrew Stainlay said the quake shook him awake at his home in Nuku'alofa in Tonga.

"The room was twisting and contorting and my cupboard smashed to the ground," he said. "When I got out of bed I was thrown against the wall."

Locals maintained it was the worst quake to hit in 20 years, though it caused little damage, Stainlay said.

"There are no high-rise buildings around here, it's mostly tin shacks," he said. "Some rusty nails might have come out, and some coconuts down from tree and when I took a drive around there were some street signs are down."

In Fiji, the tsunami alarm system only operated on the main island — not the other 110 inhabited Fijian islands. Police Insp. Penioni Ravoka of the Fijian capital of Suva said "it is difficult" to warn residents of all the inhabited islands.

About 140 guests were briefly evacuated about from the Holiday Inn hotel built on the banks of the Suva's harbor and guided about 400 meters (yards) to higher ground.

One American guest had only left hospital a day earlier after suffering a heart attack.

"Since I left all my medicine in the room we went (back) to the hospital," said Kate Morgret, of California.

The warning system failures lend greater urgency to a test of alert systems in 23 countries on both sides of the earthquake-prone Pacific that is scheduled to take place in two weeks. They will practice their emergency responses and decision-making procedures. The exercise is not expected to involve any simulated evacuations.

The quake, which struck about 16 kilometers (10 miles) at a location 2,160 kilometers (1,340 miles) north-northeast of Auckland, New Zealand, initially was assessed as having a significantly higher 8.1 magnitude.

The Hawaii center said its alerts apparently were not received in Tonga because of a power failure there that lasted about two hours.

Acting Director Gerard Fryer said, "There was problem in Tonga where there was a power outage and they didn't get our initial message." That first warning message was sent 16 minutes after the quake hit, he said.

The quake was felt in Auckland, New Zealand's largest city. Along the country's east coast, hundreds of people fled for high ground, even though no evacuations were ordered, said Richard Steel, civil defense controller in the eastern city of Gisborne.

"I would guess hundreds (of people) self-evacuated ... those television reports were a bit irresponsible," Steel told National Radio.

In Hawaii, 14 coastal schools in flood zones were closed as a precaution. Teachers and students were told to take the whole day off, but many didn't get word until they arrived at school.

Tonga — a 170-island archipelago about halfway between Australia and Tahiti — has a population of about 114,689 and an economy dependent on pumpkin and vanilla exports, fishing, foreign aid and remittances from Tongans abroad.

Fiji, a South Pacific country made up of more than 300 islands, a third of which are inhabited, is regularly rattled by earthquakes, but few cause any damage or casualties.

On Dec. 26, 2004, the most powerful earthquake in four decades — magnitude 9.0 — ripped apart the Indian Ocean floor off Indonesia's Sumatra island, displacing millions of tons of water and spawning giant waves that sped off in all directions.