A senior official of the hospital in the heart of the city, who did not want his name to be disclosed, said a letter threatening that a bomb would go off in its premises was received today.
Following this, security in and around the hospital had been beefed up, police said.
Police had yesterday received a letter warning of "powerful bomb blasts," before November 29, at the Ranganatha Swamy temple and also in the railway station and in a bus.