NEW DELHI, Nov. 6 (Xinhua) -- India's main ruling Bharatiya Janata Party (BJP) on Tuesday suffered a major setback when it lost four of the five by-polls held a couple of days ago in south Indian state of Karnataka.

The BJP could retain only one parliamentary constituency, while the ruling alliance in the state, comprising of the Indian National Congress (INC) (which is the main opposition party in the country's central politics) and the Janata Dal-Secular (JD-S) -- the main ruling party in Karnataka state, won in the rest four constituencies -- two parliamentary and two state Assembly.

Voting for three Parliamentary constituencies and two state Assembly constituencies were held on November 3. Results of the by-elections were announced Tuesday.

The biggest loss of the BJP is said to be in the Bellary parliamentary constituency which was considered as the party's stronghold for almost 15 years, as it successively won thrice since 2004. This time the candidate belonging to the INC comfortably won the constituency.

The JD-S candidate won from the Madya parliamentary constituency, while the BJP could win only in the Shimoga parliamentary constituency.

The two Assembly constituencies that went to by-polls were won by the INC and the JD-S, each.

The defeat of the BJP candidates in the four Karnataka by-polls assumes significance as the results are considered as a pointer to the possible results in the 2019 general elections, which are scheduled to be held in less than four months.

In the 2014 general elections, the BJP alone had won 282 parliamentary constituencies, but the party's strength has now left 272 only.

According to an analysis done by the "India Today" media organisation, in the past four-and-a-half years, the BJP has lost 20 by-polls out of the total 30 held since 2014.