The Delhi Police are on alert after the US-based Khalistani supporter Gurpatwant Singh Pannun released a video message threatening to "shake the very foundation of Parliament" on December 13 -- the anniversary of the 2001 terrorist attack on Parliament.

A senior police officer said security has already been stepped up in and around Parliament. "No one will be allowed to disturb law and order," he said.

"When Parliament is on, we remain alert. We are taking all precautionary measures to prevent any untoward incident," the officer said adding that security has also been beefed up in entire Delhi.

In the video, which also had a photo of the 2001 Parliament attack convict Afzal Guru, the chief of the proscribed organisation Sikhs for Justice claimed that the Narendra Modi government tried to kill him and threatened to respond on December 13.

Pannu claimed that his response would shake "the very foundation of the Indian Parliament".

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