Jakarta - Indonesia issued a tsunami warning Tuesday after a powerful earthquake struck parts of the western tip of Java and southern Sumatra province of Lampung, seismologists said.

The quake, measuring 6.6 on the Richter scale, struck under the Indian Ocean at about 10:07 am (0307 GMT), occurred at a depth of 20 kilometres, Indonesia's National Meterology and Geophysics Agency said in a short message.

The quake was located at about 125-kilometres north-west of Ujungkulon in the south-western tip of Java, about 630 kilometres south-west of Jakarta.

Indonesia's geological agency issued tsunami warnings. National TV stations broke into their programming to relay the alerts.

Indonesia, the world's largest archipelago, sits on the Pacific "Ring of Fire," the edge of a tectonic plate prone to seismic upheaval. A major earthquake and subsequent tsunami struck on December 2004, leaving more than 170,000 people dead or missing in Indonesia's Aceh province and left half a million homeless. (dpa)