About 3,000 fishermen and anti-nuclear activists in 500 mechanised and country boats tried to block the approach channel where ships enter the port but were prevented by Coast Guard and CISF personnel, CISF and port authorities said.
The protesters remained in the sea shouting slogans against central and state governments asking them to stop loading of fuel at the plant, which began on Wednesday, they said. Port activities have not been disrupted, they added.
Meanwhile, a group of anti-nuclear activists organised a human chain in Tuticorin town.
The heightened protests come against the backdrop of the Atomic Energy Regulatory Board giving its final clearance for loading of fuel in the first unit of the Indo-Russian joint venture on Tuesday.
Peoples Movement Against Nuclear Energy,' spearheading the over year-long stir, had given the call on September 20 to fishermen to stall port activities at Tuticorin, Kanyakumari, Rameswaram and Chennai today.
PMANE, whose leader S P Udayakumar is evading arrest with a non-bailable warrant against him in a case relating to the anti-nuclear stir, has also given a call to picket Central government offices in the state on September 25.
On September 10, the anti-nuclear stir took a violent turn leading to the death of a fishermen in police firing at Tuticorin.
The first unit was earlier scheduled to be commissioned in December last year but the continuing protests delayed it.