The petition requests the police and military intelligence not to harass Fr. Elil Rajendram and the families who had planned to erect a stone monument at Mullivaikkal with details of their dead relatives.
Police obtained a court order preventing the commemorative event on May 18.
AI secretary general Salil Shetty calls upon joining the campaign to prevent police harassment of Fr. Rajendram.
Several international organizations have claimed the police had summoned the cleric and members of his family several times and also searched the houses of the organizers of the event.
The London-based Sri Lanka Campaign says in the first two weeks of May alone, military intelligence had visited him six times, that he had received anonymous telephone calls in the night and that he had been summoned thrice to the police to record a statement.
The ITJP said police in Vavuniya had got him to sign a statement written in Sinhala and that his parents in Jaffna had been questioned in a threatening manner.
Right to remember the dead
The AI petition notes the Sri Lanka government has a responsibility to allow the right to remember the dead.
It requests that email, telephone, fax or twitter messages be sent to the Sri Lankan prime minister and the ambassador in the US.
The government-appointed Consultations Task Force headed by Dr. Manouri Muttettuwegama early this year recommended that the government should remove restrictions against the north-east people from remembering their dead.
According to UN statistics, at least 70,000 civilians had died in the war by the Sri Lankan government to capture the north, radiogagana.com adds.