Authorities in Japan urged people to avoid hoarding as anxiety over a possible megaquake triggered a spike Saturday in demand for disaster kits and daily necessities. In its first such advisory, the weather agency said a huge earthquake was more likely in the aftermath of a magnitude 7.1 jolt in the south on Thursday which left 14 people injured.

At a Tokyo supermarket on Saturday, a sign was put up apologising to customers for shortages of certain products it attributed to "quake-related media reports". "Potential sales restrictions are on the way", the sign said, adding bottled water was already being rationed due to "unstable" procurement. On Saturday morning the website of Japanese e-commerce giant Rakuten showed portable toilets, preserved food and bottled water topping the list of the most sought-after items.

Some retailers along the Pacific coastline also reported similar disaster-related supplies in high demand, according to local media reports. The advisory concerns the Nankai Trough "subduction zone" between two tectonic plates in the Pacific Ocean, where massive earthquakes have hit in the past. It has been the site of destructive quakes of magnitude eight or nine every century or two, with the central government having previously estimated the next big one can strike over the next 30 years roughly with a 70 percent probability.

Experts however emphasise the risk, while elevated, is still low, and the agriculture and fisheries ministry urged people "to refrain from.