Vaiko held a black-flag demonstration at Jantar Mantar here but was detained shortly after that.
The MDMK chief had opposed the invitation extended to the Sri Lankan President and had asked the Prime Minister-designate as well as BJP President Rajnath Singh to reconsider the decision.
Vaiko had earlier written a letter to Modi expressing his sadness over the invitation being extended to Rajapaksa for the event. Recalling that no Sri Lankan Head of State was invited when Atal Bihari Vajpayee was sworn in as Prime Minister, Vaiko had pointed out that even Manmohan Singh had not invited the Sri Lankan President for his swearing in ceremony.
"They did not dare to invite Mahinda Rajapaksa to the swearing in ceremony in 2004 and 2009," he had said. Tamil Nadu Chief Minister J Jayalalithaa and DMK President M Karunanidhi have also opposed the invite to Rajapaksa. The Sri Lankan President arrived this morning for the ceremony.