The court has fixed Saturday to pronounce the quantum of sentence in the case.
On August 31, 1995, then chief minister Beant Singh was killed in an explosion outside the Civil Secretariat in Chandigarh.
The Bahawalpur centre is notorious for hoarding arms and ammunition left behind by the NATO forces in Afghanistan, the officials said.
At least nine separatist organisations supporting terror groups have their bases in Canada and despite multiple deportation requests Ottawa has taken no action against those involved in heinous crimes, including the killing of popular Punjabi singer Sidhu Moosewala, officials in New Delhi said on Tuesday.
Nijjar was a close associate of Gurdeep Singh alias Deepa Heranwala, who was involved in the killing of around 200 people in Punjab during the late 1980s and early 1990s.
Sikh Federation UK, which has styled itself as one of the largest Sikh organisations based in the UK, said Avtar Singh was terminally ill with blood cancer. He was on a life support system for the last few days.
Babbar Khalsa militant Jagtar Singh Tara, convicted for life in the then Punjab Chief Minister Beant Singh's assassination, was brought in New Delhi on Friday night by a team of Punjab Police after being extradited from Bangkok.
The unidentified youths shot Nijjar, a designated terrorist, inside the premises of Guru Nanak Sikh Gurdwara Sahib, of which he was the head, at Surrey at 8:27 pm (local time) on Sunday, they said.
Jagtar Singh Hawara, a Babbar Khalsa International terrorist and his associates Jagtar Singh Tara and Paramjit Singh, all three accused in the murder for former Punjab chief minister Beant Singh, escaped after digging a tunnel in the jail.
Jagtar Singh Hawara, Jagtar Singh Tara and Paramjit Singh are the three main accused in the assassination of the Punjab chief minister in 1995.
On the run for over 10 years, Sikh militant Jagtar Singh Tara, convicted for life in the then Punjab chief minister Beant Singh's assassination, has been deported by Thailand.
Prime Minister Narendra Modi is likely to ask Britain to take strong action against Sikh groups trying to revive the demand for a separate Khalistan and their attempts to radicalise Sikh youth besides giving them training on how to make bombs.