Shiv Sena (Taksali) leader Sudhir Suri was shot dead on Friday while he was taking part in a protest outside a temple in a busy Amritsar locality, police said.
Five shots were fired at Suri after which he collapsed. He was taken to a hospital where he succumbed to bullet injuries, they said.
The accused, Sandeep Singh, has been arrested and the .32 bore licensed weapon used in the crime seized, police said.
Suri was protesting against the management of Gopal Mandir on Majitha Road -- one of the busiest places in the city -- after some broken idols of Hindu deities were allegedly found on the roadside, which he termed a sacrilege act.
The Shiv Sena leader was in the hit list of several gangsters for a long time. He was provided security by the government with around eight Punjab Police personnel being attached with him, they said.
A video of the incident in which sounds of gunshots can be heard went viral on social media. Moments before getting shot, Suri was heard explaining to police personnel the reason behind the protest.
Suri had been raising his voice against Sikh "fundamentalists" and triggered controversies in the past.
More than two years ago, Punjab Police had arrested Suri from Indore in Madhya Pradesh over an objectionable video clip allegedly denigrating women and inciting enmity between different groups, though he had denied the allegations.
Addressing a news conference in Chandigarh, Punjab Director General of Police Gaurav Yadav assured that any conspiracy behind the murder will be unveiled and urged people to maintain calm.
Yadav said the accused fired five bullets from his weapon, some of which hit Suri.
Singh, who owns a garment shop near the protest site and lives in Sultanwind area of Amritsar city, has been arrested and his questioning is underway, he said.
Preliminary investigation showed that Singh had never met Suri, the DGP said, adding that a murder case has been registered at Sadar Police station in Amritsar.
However, he refused to divulge any details about the line of investigation.
The DGP said police are investigating the murder and asserted that any conspiracy behind his killing will be unveiled.
The probe is in its early stages. Whosoever hatched the conspiracy and all those behind the murder will be arrested, said Yadav in a hurriedly called press conference.
Police will carry out the investigation on the basis of available evidence, Yadav said, adding that the situation in Amritsar is completely under control.
"Punjab has an exemplary record of communal harmony," Yadav said and appealed to people to maintain the "hard-earned peace".
"We will not allow the situation to be disturbed. We will unveil the entire conspiracy behind the murder and all those who are behind it will be arrested," said Yadav.
Speaking to reporters, Amritsar's Police Commissioner Arun Pal Singh said the accused was nabbed on the spot by Punjab Police guards attached with Suri as part of his security.
Singh's interrogation is being carried out by a team of Punjab Police officers and intelligence agencies officials to ascertain the motive behind the killing.
Tension gripped the area after news of the attack on Suri spread and some of his supporters held a protest. Suri's outfit has called for Punjab Bandh on Saturday.
After the incident, opposition Congress and BJP targeted the Bhagwant Mann-led AAP government, saying another prominent person was killed less than six months after the murder of singer Sidhu Moosewala in May.
Punjab BJP president Ashwani Sharma said the law and order has completely broken down in the state while former chief minister and BJP leader Amarinder Singh strongly condemned the "brutal murder".
"Strongly condemn brutal murder of Shiv Sena leader Sudhir Suri in Amritsar today. I appeal everyone to maintain peace and harmony and fight enemies of Punjab together. While it reflects poorly on law and order situation in Punjab, I hope culprits are given exemplary punishment," Amarinder Singh said in a tweet.
Punjab Congress president Amrinder Singh Raja Warring alleged that law and order has deteriorated in the state.
"Political differences apart, violence is unacceptable. Culprits must be brought to book," Warring said in a tweet.
Punjab BSP president Jasvir Singh Garhi alleged that instead of safeguarding Punjabis, the state police was rendering its services at the doorsteps of AAP leaders like Raghav Chadha.
"Punjab is drifting towards a dangerous direction. Due to AAP government's negligence, celebrity Punjabi singer Sidhu Moosewala was killed," Garhi alleged.
