The deceased is Anwar Hossain alias Kan Kata Ranju, 32, General Secretary of the party's Ward No 5 unit under Jagati union in Sadar upazila.

Rab officials said Ranju died of his ailment.

Ranju was an addict who was suffering from various diseases.

An accused of five different cases, Ranju was arrested by Rab at his house at Chechua village on Tuesday.

Rab recovered arms and ammunition from his possession.

Rab interrogated him for recovery of more arms.

As he fell sick critically during interrogation, he was hurriedly rushed to Kushtia General Hospital where he died on Wednesday night.

However, Ranju's family members claimed he was tortured to death by the Rab team.

Earlier, two more alleged criminals died in Rab custody here.