Singh’s tenure as Finance Minister in 1991 is particularly noted for bold economic reforms during a period of acute financial crisis.
In March, the Punjab Police booked Khan, 70, also the chief of the Pakistan Tehreek-e-Insaf (PTI) party, in the murder case, accusing him of "concealing facts and evidence" about the death of Ali Bilal alias Zille Shah, a party worker.
Khan, 70, has been in the dock for buying gifts, including an expensive Graff wristwatch, he received as the premier at a discounted price from the state depository called Toshakhana and selling them for profit.
Imran Khan's arrest came a day after the powerful military rebuked him for repeatedly accusing a senior military officer of trying to engineer his assassination and the former armed forces chief of being behind his removal from power last year.
The Islamabad police said that there was no incident of violence in the country's capital.
Manmohan Singh, 87, is under observation at the cardio-thoracic ward of the premier hospital, they said.
Feeling "humiliated" by events since demonetisation, RBI employees today wrote to Governor Urjit Patel protesting against operational "mismanagement" in the exercise and Government impinging its autonomy by appointing an official for currency coordination.