The Bharatiya Janata Party's (BJP) Manjinder Singh Sirsa on Thursday won the Delhi assembly by-election from the Rajouri Garden constituency with a margin of over 14,000 votes.

He defeated his nearest rival Meenakshi Chandela of the Congress, pushing the ruling Aam Aadmi Party's (AAP) candidate to a distant third position, according to the Election Commission.

After the final 17th round of counting, the Election Commission said that Sirsa polled 40,602 votes, Chandela 25,950 and the AAP's Harjeet Singh 10,243 out of a total 78,091 votes cast during election on April 9. Nearly 1,300 votes were divided among the other contestants.

The seat had fallen vacant after AAP's legislator Jarnail Singh resigned to contest the Punjab assembly polls on February 4 this year.

Sirsa had won this seat in 2013 assembly polls, too, but had lost to Jarnail Singh in the 2015 elections.

Elated by its victory in Rajouri Garden assembly by-polls, the BJP said that people had given the AAP a "fitting gift" by defeating it and that the party was on the verge of extinction.

"Earlier they...lost Punjab and Goa assembly polls and today's (Thursday's) result of the Rajouri Garden assembly by-poll is like the last nail in the coffin for AAP. It is on the verge of extinction," BJP spokesperson Sambit Patra said.

He added that people had lost faith in the AAP and its National Convener Arvind Kejriwal.

The BJP leader also tweeted: "AAP and Kejriwal have not just lost their deposit, they have (also) lost their credibility."

Patra said that Chief Minister Kejriwal never thought about welfare of Delhi's people.

"Neglecting Delhi people, Kejriwal went to Punjab and Goa for assembly elections. Now the residents of Delhi have neglected him," Patra told reporters.

Reacting to AAP's performance, Delhi's Deputy Chief Minister Manish Sisodia said that Rajouri Garden constituency voters were angry over AAP lawmaker Jarnail Singh's resignation to contest the Punjab assembly elections, which led to the party's poor show in the by-poll.

"People in the Rajouri Garden assembly constituency were angry after Jarnail Singh resigned... We tried to make them understand, but it seems they are still angry with the AAP," Sisodia told reporters outside his official residence.

However, he said it was just a by-poll and that "we will keep preparing for the coming elections".

The Rajouri Garden assembly by-poll on Sunday witnessed a poor turnout as only 47 per cent people turned out to vote. In the 2015 assembly elections, when the AAP had swept to power, the constituency had seen 72 per cent ballotting.

Delhi Congress President Ajay Maken termed the Rajouri Garden by-poll result a "referendum" on the Kejriwal government in Delhi.

The by-poll results showed revival of the Congress in the constituency, he added.

Maken said that the AAP's vote percentage had gone four times down to its earlier vote share, while the Congress' vote share increased three times to its earlier figure in the constituency.

"We have jumped from 12 per cent vote share for the constituency to 36 per cent in just two years," Maken said.