The Indian authorities must ensure a thorough investigation into the killing of a nun who had worked for the rights of Adivasi indigenous communities, human rights groups say.
Valsa John, aged 52, is the fourth social activist to have been killed in unexplained circumstances in India this year.
She was beaten to death by a gang of about 40 people who stormed into her home in the eastern state of Jharkhand on the night of 15 November 2011.
"Valsa John appears to have been murdered in connection with her human rights work," said Sam Zarifi, Amnesty International’s Asia-Pacific director.
"The Jharkhand authorities must ensure that those responsible for this gruesome killing are brought to justice.
“Indian federal and state authorities have to ensure that human rights activists throughout the country are protected."
Valsa John's family and human rights activists in Jharkhand told Amnesty International she had received death threats hours before her murder in Pauchuara, Pakur district.
The family told Amnesty that they believe these threats may have come from criminal gangs involved in illegal coal mining in Jharkhand.
Valsa John was jailed in 2007 for protesting against the forced acquisition of Adivasi lands for Panem Coal Mines, a coal mine project jointly operated by the Punjab state-owned Electricity Board and Eastern Mineral Trading Agency.
After being released on bail in late 2007, she reached an agreement with Panem paving the way for their acquisition of Adivasi lands, in exchange for alternate land, employment, a health centre and free education for the children of the displaced families.
Local media reported that some Adivasis were dissatisfied with the agreement.
Three other social activists have been killed this year after fighting on behalf of victims of human rights violations and marginalised communities, or using India’s Right to Information legislation to expose human rights violations and government corruption.
Earlier this month, Nadeem Sayed, a Gujarat-based activist, was stabbed to death after he testified on behalf of the victims of the Naroda Patiya massacre case in which 95 persons had been killed during the 2002 Gujarat anti-Muslim riots.
In August 2011, environmental activist Shehla Masood, aged 35, was shot dead in Bhopal city in August after trying to expose environmental violations of urban infrastructure projects and challenging mining plans in Madhya Pradesh.
In March, Jharkhand social activist Niyamat Ansari was abducted and killed after he used the Right to Information legislation to expose local contractors and officials who had embezzled funds earmarked for the rural poor.
Suspicions centre around armed Maoists because their exposure by Ansari threatened their share of the embezzled funds in return for protecting the corrupt contractors and officials.
India’s human rights organisations have been demanding new legislation to protect activists who received threats after filing petitions demanding crucial information affecting the livelihoods of local communities.
"Indian authorities must take all necessary measures to guarantee that human rights defenders and other social activists are able to carry out their legitimate and peaceful activities without fear of harassment and intimidation," said Zarifi.