Mumbai: Ram Singh alias Vijay, man accused of killing Delhi University student Radhika Tanwar, was arrested here on Saturday, four days after she was killed in broad daylight on her way to college.

The 25-year-old, whose identity was made public on Friday, was nabbed by Delhi Police from Vikhroli suburb in northeast Mumbai. He is likely to be presented before a magistrate for a transit remand and taken to Delhi.

Ram Singh is accused of gunning down Radhika, a second year student of Ram Lal Anand College. She was shot March 8 on a foot overbridge near her college in south Delhi.

The cold-blooded murder sparked widespread outrage, with even Gursharan Kaur, wife of Prime Minister Manmohan Singh, joining the chorus demanding the arrest of the killer.

Investigators had zeroed in on Singh, who introduced himself as Vijay in Delhi, after investigators detained his two friends -- Tabrez and Ashraf -- from UP's Sitapur. The duo allegedly harboured and helped him flee the capital on March 10, two days after Radhika was shot dead.

"He nurtured deep grudge against Radhika after he was beaten up for harassing her and used to tell his friends that whenever he gets an opportunity, he will take revenge. He felt insulted and left for Mumbai," H G S Dhaliwal, Deputy Commissioner of Police (South), had said on Friday.

Dhaliwal said investigations in Viswan village of Sitapur from where Vijay hails have revealed that he has a "psychopathic streak" and is learnt to have been involved in stalking women in his village. Sitapur is around 450 km from the national capital.

He returned to the capital at least 45 days ago and had followed Radhika at least twice allegedly with an intention to kill her.

"We have learnt that a month ago, he had boarded a bus in which the victim was travelling. However, he could not execute his plans. Last Saturday, he followed her on the foot-over-bridge," Dhaliwal said.

According to investigators, Vijay had gone to his friend's place in Rohini and told them he was involved in a scuffle. He stayed at their place on March eight and next day left for another friend's place in Gurgaon.