The Indian government faced growing domestic pressure on Wednesday to cool its ties with Sri Lanka, including calls for an economic embargo and for a boycott of a Commonwealth summit in Colombo.
Politicians in Tamil Nadu, which has seen daily protests against Colombo, passed a resolution on Wednesday asking New Delhi to stop treating Sri Lanka as a friendly country until it probes the "genocide" of ethnic Tamils.
The resolution also called on India to operate an economic embargo against Sri Lanka, a day after chief minister J Jayalalithaa barred Sri Lankan cricketers from playing any matches on her patch.
Sri Lanka's sports minister retaliated, saying the country would not allow its cricketers to travel to India to play in the IPL Twenty20 tournament next month unless it gets guarantees from New Delhi of their safety.
Tamil Nadu also demanded an international probe into the alleged "genocide" of Tamils in Sri Lanka, and asked New Delhi to move a UN resolution seeking a referendum on creating a separate homeland for the minority community.
As anger deepens among Indian Tamils about Colombo's treatment of their ethnic kinsmen, politicians in both Tamil Nadu and the neighbouring union territory of Pondicherry have insisted on stronger action by New Delhi.
Pondicherry chief minister N Rangasamy said he would petition the central government to boycott the Commonwealth Heads of Government Meeting in Colombo in November.
"We will write to the Centre to urge that India skip the meet at Colombo. We will write the letter to the centre immediately," PTI quoted Rangasamy as telling local lawmakers.
The issue has already proved toxic for the central government, with the Tamil Nadu-based Dravida Munnetra Kazhagam party quitting the ruling coalition last week after accusing it of being soft towards Colombo.
Rights groups have said Sri Lankan troops killed up to 40,000 members of the minority Tamil population in 2009 in the final months of the island's civil war, a charge denied by Colombo.
The Indian government, which has traditionally been wary of upsetting its neighbour, was among 25 nations which last week supported a resolution at the UN Human Rights Council calling for a probe of alleged war crimes on the island.