Stepping up their protest against the Kudankulam nuclear power plant, thousands of fishermen laid siege to the Tuticorin port - located 100 km from the nuclear plant - on Saturday.
Nearly 600 fishing boats assembled from the coastal districts of Kanyakumari, Tirunelveli and Ramanthapuram and blocked the shipping channel.
The blockade, which began in the morning, continued till 2 pm despite the pleas of Union shipping minister GK Vasan.
The protest disrupted port activities for over two hours.
P Udayakumar, convener of the People's Movement Against Nuclear Energy (PMANE), against whom non-bailable warrants have been issued by a local court, surfaced at a nearby fishing hamlet and led thousands of villagers into waist-deep sea waters to stage a jal satyagraha.
Besides, in coastal areas of southern Tamil Nadu, protesters formed human chains.
The agitation has been stepped up after the Atomic Energy Regulatory Board gave its final clearance to load enriched uranium fuel rods in the first reactor of the plant.
"How can they remain silent spectators despite mounting protests the government is going ahead with fuelling? It is nothing but murder of democracy," said Udayakumar.
The coordination committee, he said, would meet on September 27 to announce fresh modes of agitation.
The plant had run into a series of protests in the wake of the last year's Fukushima nuclear disaster in Japan.
The year-long peaceful agitation had turned violent two weeks ago, when police firing claimed a life. Though arrest warrants have been issued against most of the PMANE leaders, they are yet to surrender.