About 400 police personnel equipped with different types of arms and ammunition, speedboats, launches, trawlers and fishing boats are conducting the drive against the criminals, who use the world's largest mangrove forest as their safe haven.

The four districts are Pirojpur and Barguna under Barisal range and Bagerhat and Khulna in Khulna range. The deputy inspector generals of the two ranges are guiding the operation.

Reports received till yesterday evening said, at least 17 criminals including two absconding convicts and eight wanted ones were arrested.

The operation is being guided from command posts set up in the region.

But police are maintaining strict secrecy about the drive and officially described it as a routine activity to arrest the criminals involved in the recent Bhandaria Bandar looting and recover the looted items.

According to sources, gangs of criminals hiding in the forest abducted more than 150 people including honey collectors, woodcutters, fishermen and visitors to the forest. For the safety and recovery of the abducted people, Tk 5,000 to one lakh per head were paid to the abductors.

At least five persons were killed and six injured in fights between forest guards and the criminals.

The sources said at least 13 gangs of pirates and dacoits have their dens in the Sundarbans. Notorious gangleaders like Master, Razzak, Mannan, Rezaul and Kalu created panic in the region.

The areas with such dens include Supati, Mela, BadamTala, Tiar Char, Jhapa, NandaBala, CharKhali, Chandeswar, Shapla, KochiKhali, KalamiarVarani, Dasher Varani, Dudh Mukhi, Sholar Char, Tabul Bunia, Sindurer Kouta, Har Karia, Dhan Shidhdha, Dhan Shagor, Maitta and Badamtala.