"The government of Sri Lanka is constrained to request Sri Lankan nationals in the interest of their security to desist from undertaking visits to Tamil Nadu until further notice," the external affairs ministry said.

As well as the incident involving the pilgrims, the ministry highlighted how two Sri Lankan football teams visiting Tamil Nadu for friendly matches had been asked to leave.

Sri Lankan military personnel undergoing training in the Tamil Nadu state had also been forced out, it said.

Politicians in Tamil Nadu have been highly critical of Sri Lanka's government over its military campaign that defeated separatist Tamil Tiger rebels in May 2009.

Tamil Nadu was a base for Sri Lankan Tamil rebels during the early days of their guerrilla war in the 1980s. Indian Tamils share close cultural and religious links with Sri Lanka's ethnic Tamil minority.

Sri Lanka said it was attempting to assure the safety of the besieged pilgrims, but the Press Trust of India (PTI) news agency reported that they were harassed for a second day on Tuesday.

Indian police intervened and arrested nine activists of a pro-Tamil rebel party who tried to block the seven buses carrying Sri Lankan pilgrims as they returned from the Velankanni Christian shrine on Tuesday, PTI said.