Chennai, Jun 9 (IANS): DMK president M. Karunanidhi Sunday told Prime Minister Manmohan Singh that India has to ensure the implementation of a 1987 pact with Sri Lanka that promised autonomy to the Tamils there.

In a letter to Manmohan Singh, the former Tamil Nadu chief minister referred to attempts by "Sinhalese extremist groups" in Sri Lanka to get the 1987 Rajiv Gandhi-Junius Jayawardane accord abrogated.

"India should not be a silent spectator to the events taking place in Sri Lanka at this critical point of time," Karunanidhi said.

He said the Sinhalese extremists were planning to conduct protests until President Mahinda Rajapakse takes action to repeal the India-backed 13th amendment to the Sri Lankan constitution and cancel the proposed election in the Tamil-majority northern province.

Karunanidhi said the 13th amendment was a direct consequence of the India-Sri Lanka pact under which New Delhi deployed troops in the island's northeast to battle the Tamil Tigers.

"We, in India, have promised the Sri Lankan Tamils through this accord that we will underwrite and guarantee implementation of the accord," Karunanidhi said.

According to him, the inflow of Tamil refugees from Sri Lanka was draining the state's resources and over 225,000 refugees were waiting to return.