A Mumbai-based man was arrested for allegedly sending a threatening e-mail to businessman Sunjay Kapur, the estranged husband of Bollywood actor Karisma Kapoor.

Rajkumar alias Rajubhai was arrested by the Delhi police's Special Cell from Mulund in suburban Mumbai on Tuesday evening where he ran a cyber cafe. 

He had allegedly sent the e-mail last week threatening to kill Kapur if he did not pay Rs 50 crore (Rs 500 million). 

Rajkumar has been brought to Delhi and interrogated by the police.

Police sources said Rajkumar had no link with Karisma, who has been embroiled in a tussle with her husband over the custody of their five-month-old daughter Samaira. 

Sunjay had alleged that Karisma got a passport issued to their minor daughter without his consent and that she was planning to leave for the US along with Samaira without taking him into confidence.