He said India has full faith in the Afghan investigation agencies and they have informed that so far 6-7 people have been arrested in the case. Last week, a renegade Taliban militia, the suicide group of the Islamic Movement of Afghanistan, took responsibility for killing Banerjee, claiming she was an "Indian spy".
"We killed Sushmita Banerjee because she is an Indian spy," the group's spokesman Qari Hamza had told The Daily Beast, the online home of Newsweek magazine.
Banerjee, 49, was married to Afghan businessman Jaanbaz Khan and recently moved back to Afghanistan to live with him.
However, she was killed by militants in eastern Paktika province of Afghanistan earlier this month. Banerjee's book Kabuliwalar Bangali Bou (A Kabuliwala's Bengali Wife), about her escape from the Taliban in 1995, became a bestseller in India and was made into the Bollywood film "Escape From Taliban" in 2003.
The memoir focused on her life in Afghanistan with her husband and her escape from the militants.