But the bomb the attackers blasted in Laxmipur to make their escape way had some similarity with those of August 17.

"The one that went off inside the courtroom was different, quite stronger and more destructive," said Laxmipur Superintendent of Police (SP) Fazlur Rahman.

But the one blasted on the stairs was not as strong as others, which was connected to a battery like the ones in the August 17 bombs although no wire or detonator was found, he said.

A time device was used in the August 17 blasts, but yesterday's bomb had no such device.

"Today's bombs exploded just after those were hurled," the SP added.

Talking to The Daily Star, Chandpur SP BM Harunur Rashid said two bombs hurled at the Chandpur court premises were stronger than those blasted and recovered on August 17.

"These were powerful. The splinters used in those bombs were much more destructive," he said.

All four bombs were locally made.

Although the army bomb squad was likely to reach Chittagong to examine two recovered bombs and the remains of a blasted one, nothing could be known about those as of the filing of this report late last night.

A team of Rab's bomb squad, meanwhile, went to Chandpur and Laxmipur for bomb examination.