A 6.5 magnitude earthquake struck in the vicinity of the Kermadec Islands north of New Zealand, the U.S. Geological Survey said on its Web site. There were no immediate reports of a tsunami after an alert was issued.

The earthquake struck at 3:15 p.m. local time at a depth of 53 kilometers (33 miles), 1,050 kilometers northeast of Auckland, the USGS, which characterized the tremor as ''strong,'' said on its Web site. In an initial e-mailed alert the USGS put the depth at 33 kilometers.

The Pacific Tsunami Warning Center, which put the magnitude at 6.6, issued a tsunami alert for areas within ''a hundred kilometers'' of the quake zone. There was no threat of a large Pacific-wide tsunami, it said. There were no immediate reports of damage or of a tsunami.

The Kermadec Islands, New Zealand's biggest marine reserve, are uninhabited apart from employees of the Department of Conservation who run a weather station there, according to the department's Web site. The weather station is located on Raoul Island, the northernmost of the island chain.

The islands lie in a zone where the Pacific and the Indo- Australian Plates meet. These tectonic plates constantly shift, sometimes causing earthquakes, some of them producing tsunamis. Quakes of magnitude 5 or greater can be destructive depending on their depth.