Authorities, who earlier relied on low-tech ways to spread alerts, will now be able to send instant warnings via sirens of imminent tsunamis, volcano eruptions or other disasters.

The new system, known as J-Alert, will soon be expanded to warn residents of approaching missiles and earthquakes, which Japanese meteorologists can predict seconds before they occur.

"We are preparing to be able to give missile alerts by this summer," said Fire and Disaster Management Agency official Takashi Ito.

Japan is one of the most quake-prone nations in the world, with its cities constantly living in fear of "The Big One."

It has also been boosting its missile defences in cooperation with the United States since North Korea fired a long-range missile over Japan's main island into the Pacific in 1998.

The J-Alert's trial launch took place, with some hiccups, in the western city of Kobe, which suffered a giant earthquake in 1995 that killed almost 6,500 people.

In the drill, disaster authorities relayed news of a medium-size quake to Kobe's Ichikawacho area.

On the second try, radio speakers installed in public places sounded a hypothetical alert to leave, a town official said.

"Before we introduced the new system, we had to depend on local officials to relay emergency information to households, sometimes in a primitive way like getting in their cars and driving around to alert residents," Ito said.

"But we wouldn't have that much time to evacuate in such events as a missile attack," Ito said. "With the new system, we could give alerts to people much more quickly."

Four cities and 10 of Japan's 47 prefectures will initially receive the satellite alert system, which will be expanded to 80 percent of the country by March 2009, the disaster agency said.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.