Rab yesterday arrested the wife of Maruf Reza Sagar who was reportedly with Jubo League leader Reazul Haque Khan Milky when he was murdered.
Sagar took Milky to Gulshan in his own car from the latter's Mohammadpur residence on July 30, police said.
Rab 1 officials said Sagar's wife, Fahima Islam Lopa, 25, was arrested at her Dhanmondi residence on Saturday afternoon for assisting Jubo League leader Zahid Siddiki Tarek, who was the key accused in Milky murder case.
Tarek was killed by Rab "crossfire" only hours after his arrest.
She will be produced at a Dhaka court on Sunday.
A gang of armed criminals gunned down Milky, a former organising secretary of Dhaka city (south) Jubo League, in front of Shoppers World in the Gulshan area.
"Lopa provided Tarek with updated information about Milky's location after talking to her husband Sagar, who always accompanied Milky," said Lt Col Ziaul Ahsan, director of the intelligence wing of Rab.
"As per Lopa's information, Tarek and his gang first took position near Bhasabi Shopping Mall. But, having failed, he made the second attempt in front of Shoppers World."
Asked, he claimed: "Lopa was angry with Milky as her husband remained busy with him. Besides this, she had a relationship with Tarek for the last one year."
The Rab official said Lopa claimed that Tarek had first decided to kill Milky one year ago, but finally planned it a month ago.
"Since then, she had been providing Tarek with information about Milky's location after talking to her husband."
Earlier, in the mid July, Tarek had wanted to kill Milky during the four-day hartal enforced by Jamaat-e-Islami.
Rab members arrested Tarek, a former joint secretary of the same unit of Jubo League, at a clinic in Uttara, along with six others in connection with the Milky murder.
