The Ghaziabad police said the station superintendent had received the letter yesterday by post. The sender "has threatened to target Narendra Modi, L K Advani, Akhilesh Yadav, Mayawati and other leaders on June 20", Superintendent of Police (City) Shiv Hari Meena told PTI.
Meena said the local police had shared the details of the letter with state intelligence agencies. "We are trying to trace the person who sent the letter by post," he said.
"We are also investigating if somebody has sent it to make fun, and will be interrogating postal department officials to ascertain from where it was sent," he said.
The sender has also threatened to plant bombs in several railways stations and temples. As per the letter, railway stations in Delhi, Ghaziabad, Bulandshar, Kanpur, Mathura, Bhopal and among others will be targeted on June 15.
Meena said the sender also threatened to plant bombs in Kali Mata Mandir in Delhi, Dudeswar Nath Temple and Janaki Temple in Ghaziabad.
The Ghaziabad police has sounded an alert and security has been beefed up at railways stations and temples. Police today carried out checks at railways stations and temples, and frisked passengers and temple-goers.