The bomb that went off in Chittagong was almost similar to those blasted on the Chittagong court premises on October 3, while the Gazipur bomb resembled the one used at Jhalakathi on November 14.

Besides, the bomb-makers of the October 3 attacks and yesterday's were also same, the bomb experts believe.

Our Chittagong correspondent quoting police and army experts said the bomb contained highly powerful plastic explosives.

Deputy Commander of Rapid Action Battalion-Chittagong Major Sharif told The Daily Star that he believed the bomb was lightweight for easy transportation yet capable of wrecking a havoc.

"However, it is too early to comment on its type. Something specific about its composition and ingredients can only be said after we complete examination of the samples collected from the spot," he said.

The explosives experts, meanwhile, told The Daily Star that powerful homemade explosives have most probably been used in the bomb that went off in Gazipur.

Electronic detonator and circuit were used to detonate the bomb as was done in the August 17 bomb blasts and in Jhalakathi.

Pieces of iron used in fishing nets have been used as splinters in the Gazipur bomb. Shrapnel collected from the spot weigh about 3 kg, with each piece weighing about 20-25 grams.