Australian nuclear experts raised concerns Monday that unsecured sources of radioactive waste in medical centres in Southeast Asia could be used by militants to build a "dirty bomb."

Experts from the Australian Nuclear Science and Technology Organization (ANSTO), who have checked radioactive waste in Southeast Asia for the past year, said cobalt was found unsecured in two countries after radiation therapy centres closed.

"This is all to do with preventing there ever being a dirty bomb," ANSTO chief of operations Ron Cameron.

About 25 other radiation centres are being investigated in a third country, The Australian newspaper reported.

Cameron declined to name the countries involved, but said Asian governments needed to do more to guarantee the safe disposal of the material, common in cancer treatments in major hospitals.

He said without stronger security and disposal rules, there was a risk militants could find the radioactive material and use it to build a weapon capable of contaminating a large area of a major city.

Conventional explosives wrapped around radioactive material could make a so-called dirty bomb, which would do little immediate damage but could spread radioactive material across a city, causing panic and an increase in cancer rates.

Cameron said radioactive cobalt and caesium were the most common materials, and were used in the mining and gas industries and in radiation treatment for cancer patients.

A team of 10 ANSTO experts are training officials from 11 Southeast Asian and Pacific island nations under a three-year programme to help countries find and secure radioactive waste.

Source: China Daily