New Delhi, Jun 21 (IANS): An anonymous letter threatening to attack Prime Minister Narendra Modi has put all security agencies on the toes.

The letter was received in the office of a temple in Thrissur district of Kerala during PM Modi's visit last fortnight.

Highly placed sources in the agencies said the letter was received at the office of Guruvayur temple on June 7, close to the PM's visit to Kerala.

"The content of the letter initially caused panic as the PM was scheduled to visit the same temple. The temple authorities informed us about the letter and subsequently security was put on high alert," a senior official of Kerala police told IANS.

As per a confidential report of the Intelligence Bureau, shared with Special Protection Group and police of relevant states, the "threat message was written in Malyalam on a Rs 500 note sealed in an envelop." A few words in English were also written. The source of the letter is being traced, a police officer added. For security reasons, IANS cannot share the entire text of the threat message.

According to intelligence sources, Prime Minister's security arrangements are always as per the security blue book and all efforts are made to provide foolproof security cover to the executive head of the state. Any message relating to any sort of threat to the PM is evaluated by different agencies at various levels.

The SPG, which forms the inner cordon of PM's security, constantly coordinates with intelligence agencies, local and the state police. About raising the level of PM's security in wake of the recent threat, an official said, though people are concerned about the PM's security, such details cannot be shared with the media.