Activists belonging to pro-Tamil organisations including Aathi Thamizhar Peravai and Naam Tamizhar Iyakkam earlier blocked the road demanding that the Union Government vote against Sri Lanka at the United Nations Human Rights Council (UNHRC) meeting in Geneva, officials said.
They also shouted slogans against the Sri Lankan President Mahinda Rajapaksa for alleged war crimes against ethnic Tamils.
The glass windows of the office, located in a city hotel, were damaged, and further inquiry was on, police said, adding, 30 people have been arrested.
Yesterday, about 40 students of a government law college here allegedly damaged a party flag post and notice board of Janata Party office here, protesting its chief Subramanian Swamy's recent meeting with the Lankan President.