Mumbai Police has stepped up vigil after an anonymous letter sent to the state Secretariat 'Mantralaya' threatened to bomb important government installations in Mumbai and Nagpur.

The letter, received yesterday, specified timings at which the places will be bombed, sources said, adding that it mentioned Mantralaya, Vidhan Bhavan, MLA hostel, Manora Hostel and Nagpur Vidhan Sabha as the targets.

The state secretariat officials informed about the threat letter the police, who sounded a high alert in south Mumbai.

A check was carried out all important places and vehicles, including those parked at the places mentioned in the letter, were thoroughly checked, police said.

As the timings mentioned in the letter for the attacks passed by, police said it appeared that the letter was a hoax.

However, checking has been stepped up and the letter would not be taken lightly, police said.