India has paid tribute to the former prime minister, Indira Gandhi, on the 20th anniversary of her assassination.
Prime Minister Manmohan Singh was among those at the memorial
Prime Minister Manmohan Singh, a Sikh, and Congress party president Sonia Gandhi, Mrs Gandhi's daughter-in-law, led tributes at a memorial in Delhi.
They sprinkled rose petals on the rock memorial and attended prayers at the residence where she was killed by her Sikh bodyguards in 1984.
Mrs Gandhi was prime minister from 1966 to 1977, and from 1980 to her death.
An international human rights group has urged the Indian government to make a public commitment to prosecute those responsible for the anti-Sikh violence that followed her death.
"After two decades, the prosecutors and police should act. There is more than enough evidence to do so now," said Brian Adams, Asia director of Human Rights Watch, said in a statement.
Some of those responsible for the violence had been, and still were, members of the governing Congress Party, the New York-based group said.
Seven government-appointed commissions which had investigated the massacres were either whitewashes, or had met with official obstruction, it added.
Official estimates say more than 2,700 Sikhs died in riots which erupted across India in the days following her murder, as Hindus took their revenge on Sikhs who were blamed for the assassination.
Civil rights groups say nearly 4,000 died.
Publication of the latest report on the violence, by the Nanavati Commission, was due on Monday but is reported to have been put back by two months.