Polling will be held on Thursday from 7 a.m. to 6 p.m. and votes count will be counted on December 9.
"We have directed political leaders, workers and poll campaign managers who are not voters in the poll-bound areas to leave the area and candidates have been advised not to use loudspeakers during the 48-hour silent period," the official said.
The candidates and their supporters, however, can canvass door-to-door on Wednesday and appeal to voters to cast their ballot on Thursday.
The by-elections were necessitated due to disqualification of 14 Congress and 3 JD-S rebel legislators after they resigned from the Assembly in mid-July in protest against the then JD-S-Congress coalition government's functioning.
The by-elections will be held in Athani, Kagwad, Gokak, Yellapura, Hirekerur, Ranibennur, Vijaynagara, Chikkballapura, K.R. Pura, Yeshwanthpura, Mahalakshmi Layout, Shivajinagara, Hosakote, K.R. Pete and Hunsur.
By-elections in two assembly segments -- Muski (Raichur district) and R.R. Nagar (Bengaluru) have been withheld due to litigation in the Karnataka High Court over their results in the May 2018 stare assembly elections.
As many as 165 candidates, including 126 Independents and 9 women are in the fray for the 15 assembly seats.
The BJP and the opposition Congress are contesting in all the 15 assembly seats, while the JD-S has fielded candidates in 12 seats.
The BJP has fielded 11 former rebel Congress and 3 former rebel JD-S legislators who joined the party on November 14 after the Supreme Court on November 13 allowed them to re-contest though it upheld their disqualification by then Assembly Speaker K.R. Ramesh Kumar.
The BJP has fielded its former corporate Sarvana from the prestigious Shivajinagara constituency in Bengaluru central.
For the ruling BJP, Chief Minister B.S. Yediyurappa, three Deputy Chief Ministers G.M. Karjol, Ashwath Narayan and Laxman Savadi and dozen cabinet ministers campaigned along with hundreds of party cadres and supporters.
For the Congress, its former Chief Minister Siddaramaiah, party's state unit president Dinesh Gundu Rao and other senior leaders, including Mallikarjun Kharge and D.K. Shivakumar participated in the electioneering.
JD-S supremo H.D. Deve Gowda and his son and former Chief Minister H.D. Kumaraswamy led the party's campaign with senior leaders and legislators in the 12 assembly segments it is contesting.