A Sikh activist marking the anniversary of the killing of British Columbia temple leader Hardeep Singh Nijjar says the past year has shown they are vindicated in their claims that India targeted separatists overseas.

Gurpatwant Singh Pannun, a New York-based activist who himself was targeted by India according to U.S. authorities, says Nijjar's murder a year ago was "not the kind of publicity" the Sikh independence movement was seeking.

Pannun says Nijjar's death and subsequent revelations by Canadian and U.S. officials have "uncovered" India's plans to silence overseas dissidents with violence outside the law.

Nijjar, a key organizer for an overseas referendum on an independent Sikh state in India, was gunned down in the parking lot of the Surrey, B.C., temple where he was president on June 18 last year.

Sikh activist groups are marking the one-year anniversary of his death with a rally and a "citizens' court" outside Vancouver's Indian consulate, as well as a commemoration at Guru Nanak Gurdwara in Surrey where he was killed.

Four Indian nationals Karan Brar, Amandeep Singh, Kamalpreet Singh and Karanpreet Singh are accused of murder and conspiracy in Nijjar's killing last year which strained relations between Canada and India.

Prime Minister Justin Trudeau told Parliament that credible intelligence linked Nijjar's death to Indian government involvement.

Pannun says activists are pushing ahead with holding non-binding referendums in overseas Sikh communities on the question of creating an independent state known as Khalistan, with the next vote slated for Calgary on July 28.

"Even though we have lost Shahid Nijjar as our main co-ordinator, we are continuing on with full resolve on the path of independence," Pannun says, using the Sikh term for martyrdom in reference to the Surrey temple leader.

"If the cost of running or organizing a Khalistan referendum is a bullet, I'm ready to face that bullet," he says.

India has denied involvement in the killing and says it does not have a policy of assassinating people abroad.

The four accused in the case are next scheduled to appear in court in Surrey on June 25.