An earthquake with a magnitude 7.5struck off Papua New Guinea on Saturday and a tsunami warning was briefly issuedfor the Pacific Island nation and neighbouring Solomon Islands, but there were noimmediate reports of damage, according to Reuters.The quake, at a depth of 10 km (6 miles), struck 68 km southwest of Panguna on theisland of Bougainville, the U.S. Geological Survey said, revising down the magnitudefrom an initial 7.8.The Pacific Tsunami Warning Center later cancelled a tsunami warning for PapuaNew Guinea and the Solomon Islands and there was no threat to neighbouringAustralia or across the Pacific Ocean.At least six strong tremors have hit near Bougainville in the past week or so,including a magnitude 7.3 on April 11, but there have been no reports of major damage.