The new arrests, announced in a statement released by Scotland Yard, bring to 15 the number of people detained since Kuldeep Singh Brar had his neck slashed by assailants on London's busy Oxford Street shopping area on Sunday. Brar has told Indian media that he believes the stabbing was carried out by Sikh extremists in revenge for his role in the attack on the Golden Temple in Amritsar in 1984, a bloody assault in which more than 1,000 people were killed.
The statement said that while Scotland Yard was aware of speculation over the attackers' motives, "it would not be helpful to our investigation to comment further at this stage."
The storming of the Golden Temple was one of the most violent episodes in the Indian government's battle against Sikh separatists, whose campaign for an independent homeland in the Punjab region of India smoldered into the 1970s and 80s.
The Indian army's attack on hundreds of heavily armed Sikh separatists barricaded inside the Golden Temple led to massive loss of life and a breakdown in communal relations across India. Later that year, Indian Prime Minister Indira Gandhi was assassinated by two Sikh bodyguards, and the country was swept by a
Although the Sikh separatist movement has since lost much of its force, there are still occasional acts of violence.
Scotland Yard said that all eight suspects, whose ages range from 20 to 42, were arrested at various addresses in west London in the early hours of Friday. Six were arrested on suspicion of conspiracy to murder; two were arrested on suspicion of assisting an offender.
The police service says officers investigating the stabbing had detained a further three people on suspicion of immigration offenses unrelated to the attempted murder investigation.
Friday's arrests follow the detention of four people on Thursday.