More than 2,500 aftershocks have been observed after a strong earthquake occurred on Dec. 26 off the west coast of the Indonesian island of Sumatra, the Comprehensive Test Ban Treaty Organization (CTBTO) said Thursday.

"1,500 aftershocks were recorded in the 48 hours that followed the quake, and 1,000 since then," said CTBTO spokesman Bernhard Wrabetz.

He added that one of the strongest aftershocks, measuring 5.4 on the Richter scale, was recorded Wednesday off the Sumatra island. CTBTO experts say that the tremors will continue for several months but become more and more sporadic.

The CTBTO has set up a sensor network throughout the world which can be used to detect any nuclear tests that violate the 1996 treaty and monitor natural seismic activity.

The massive earthquake and ensuing tsunamis have claimed the lives of over 145,000 people in Asia and Africa.

(Xinhua News Agency January 7, 2005)