The victims included an Australian NRI woman, who came here to attend a marriage, police said.
The victims, hailing from the fishermen colony of Periyapattinam village, were on a picnic between Rameswaram and Tuticorin in a boat fitted with engine when the mishap occurred,
Marine Police DSP Thiagarajan said.
It was not known immediately how many people were travelling in the boat though it was permitted to carry upto seven passengers only.
Preliminary reports said the boat carried more than 20 people, he said.
A top official of the Indian Coastguard told PTI that rescue and search operations by naval helicopter and Coast Guard's hover crafts and Marine Police were going on as there were different versions about the number of passengers.
People from the village had proceeded in two boats, one of which capsized, Thiragarajan said.
The boats were owned by Abyub Khan and Rasool Khan and they were not licenced to carry people.
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