Japanese mobile telephone users may soon be warned of an earthquake in their area before it even strikes. Japan's two biggest operators, NTT DoCoMo and KDDI, said Wednesday they are jointly developing a system to notify customers of an imminent earthquake, while number three Softbank said it is separately working on a similar service.

The system, which is expected to go into operation within a few months, will pass on information from the Japanese meteorological agency which has developed a way of detecting earthquakes several seconds before the main tremor strikes.

The meteorological agency's early-warning system detects the first underground tremors that come before the main quake and estimates their intensity before big seismic waves reach the surface.