WELLINGTON, New Zealand — Several real earthquakes hit the geologically unstable Pacific region where scientists were testing a tsunami-warning system — including a powerful one yesterday north of New Zealand that generated a real tsunami, albeit a small one.

There also were three quakes off the coast of Indonesia and two off the island nation of Tonga. No damage or injuries were reported.

The latest, a magnitude-5.8 earthquake this morning, rattled Tonga at the same time that emergency authorities on the country's islands were broadcasting simulated earthquake alerts as part of the Pacific-wide simulation. The quake was the latest in a string of aftershocks to hit the country since a powerful 7.8 quake on May 4. A magnitude-5.1 quake struck Tonga early in the day as well.

The largest quake, at 12:39 a.m. Hawai'i time yesterday, was centered about 710 miles northeast of New Zealand's largest city, Auckland. New Zealand national civil defense controller Mike O'Leary said the minor local tsunami it generated did not affect any populated areas.

Later, last night, a magnitude-6.8 earthquake struck western Indonesia off the coast of Nias island. It was followed by two smaller aftershocks, according to the USGS. No substantial damage was reported.