Meanwhile, a Danish minister thanked the Bangladesh government for its efforts in rescuing Suman.

Sources in the law enforcement agencies said their main objective is to capture the masterminds of the abduction. They claimed they are trying to zero in on the criminals by reducing the cordoned off area.

Security officials in the district said they sent more army personnel by helicopter to Yangrai, Choto Modok and Tindu areas in order to reinforce the army units there.

Eighteen people have been arrested since Suman was abducted on June 25. Interrogators said they found incriminating evidence that a number of them were involved with the abduction.

Non-government organisations have stopped their activities at Thanchi upazila and in some other areas of the district since Suman's abduction. However, law enforcers said they had not imposed any restrictions on NGO activities.

Danish Minister for Development and Cooperation Ulla Tornaes yesterday thanked the Bangladesh government for "the excellent cooperation it had extended" in rescuing the Danida personnel, BSS reports.

Tornaes conveyed her government's gratitude by making a telephone call to Foreign Adviser Iftekhar Ahmed Chowdhury from Copenhagen.

Iftekhar expressed deep appreciation of Denmark's sustained support to Bangladesh's development efforts, and said Bangladesh looks forward to expanding political, economic and cultural relations with Denmark.