Police on Saturday sounded alert in the city after a mysterious letter threatened of multiple bomb blasts in different places, including the Raj Bhawan and the Chief Minister's residence.
Security around the vital installations has been stepped up and thorough checking was on across the city, police said.
The letter, received by Churchgate railway station master, threatened of bomb blasts either on November 14 and November 28, a senior police official said adding all security agencies were on alert.
Adequate security measures have also been taken on the occasion 'Bakr Eid' on Saturday, the officer said adding, "On November 14, we were on alert and luckily nothing happened. We are checking vehicles and security at railway stations has been tightened. We do not want to take any chances today, it being a festival day."
The letter received on November 8 was written in Hindi and posted from Kanyakumari in Tamil Nadu, the police said.
The letter claimed explosions would occur at Vidhan Bhavan, residences of the Governor and the Chief Minister, RBI and landmark Taj Mahal and Oberoi hotels in South Mumbai. The letter also claimed explosives have already reached three different locations in the metropolis and five to six persons had been given the responsibility to execute the blasts.
The letter has named two persons Arvind Singh Arora and Bhupinder Singh Arora who it says have hidden explosive material, including RDX, near Bhabha Farid Institute of Technology in Dehradhun in Uttarkhand.