New Delhi, Nov 12 The National Investigative Agency (NIA) on Thursday has registered a case against suspected terrorist Pakistan born US citizen Headley and his aide Canadian born Tahawwur Hussain Rana in connection with the 26/11 Mumbai attacks.

Addressing the media here, Union Home Minister P Chidambaram said government agencies are probing both Headley and Rana's terror links in India.

He also revealed that Headley not only visited India several times between 2006 and 2009, but he also came once after the 26/11 attacks.

"It is true that David Headley visited several times before 26/11 and once after 26/11, and we are investigating." Chidambaram said.

He also said that inquiries were being conducted in the cities the Headley visited.

"There is a fresh terror alert after sources said on Wednesday that Headley had visited five cities in India and that there was the threat of multiple and simultaneous attacks in these cities," Chidambaram added.

Headley was arrested by the US Federal Bureau of Investigation ( FBI) on October 3 and details shared with Indian intelligence officials show that his plot in India included the National Defence College in New Delhi, two elite boarding schools Woodstock and The Doon in Uttarakhand and the Taj Mahal among others.

FBI Director Robert Swan Mueller, who is scheduled to visit India from November 18, is expected to share more details of LeT's foiled Indian plot with Chidambaram. (ANI)