The killing of a 22-year-old Indian fisherman shot dead near Palk Strait allegedly by Sri Lankan Navy personnel has put the focus back on a tiny island of Kachchatheevu that the Tamil Nadu government alleges was wrongly ceded to Sri Lanka through two pacts signed between New Delhi and Colombo in the 1970s. Sri Lanka has denied its Navy was involved but tried to cap the tragedy from straining relations between the two neighbours. It said a thorough probe would be held along with Indian authorities and echoed India's "deep concern" at the killing. But an angry, and impatient Tamil Nadu - that saw a bitter struggle for power in February - wants the Centre to do more to put pressure on Colombo.