"We have arrested Milan Kumar Sarkar and Wahidul Islam from Sealdah station (Main) last night," the official said.
"Acting on a tip-off, we had laid a trap and when the duo arrived at the station, we arrested them," the official said adding, "both are Bangladeshi nationals and they don't have any valid passport or document."
The Sister Superior of Jesus and Mary's Convent School was gangraped by dacoits at Ranaghat in Nadia district on March 14.
Earlier one person was arrested from Mumbai and two others were nabbed from West Bengal.
The investigation into the involvement of the arrested duo was on, the official said.
Apart from brutalising the nun, the criminals had also looted Rs 12 lakh in cash from the convent's coffer.