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

Such 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.

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.