Chennai, Aug 17 (IANS): DMK president M. Karunanidhi Saturday warned of rail blockades, black flags on houses and commercial establishments across the state if Prime Minister Manmohan Singh did not declare that India would not participate in the Commonwealth Heads of Government Meeting (CHOGM) in Colombo.

Sri Lankan Foreign Minister G.L. Peiris is slated to arrive in New Delhi Sunday to invite Manmohan Singh to attend the meeting.

In a statement issued here, Karunanidhi, referring to Peiris' proposed visit - said: "The prime minister without neglecting Tamils' demand should categorically and openly declare that India will not participate in the meet."

Karunanidhi said if the centre neglects this request, then the DMK would carry out rail blockades and hoist black flags atop houses and commercial establishments protesting India's decision.

He said the Lankan government has lost credibility in the international forum and it is trying to dilute the provisions of 13th amendment to its constitution.

The 13th amendment in the Sri Lankan constitution was carried out with Indian backing in the 1987 to ensure autonomy to provinces and by extension to the Tamils in the island's north and east.

But the regime of President Mahinda Rajapaksa has threatened to dilute its provisions, causing dismay in India.