In one of the biggest drugs haul, an Indian Coast Guard (ICG) ship seized 1,500 kgs of heroin valued at about Rs 3,500 crore from a merchant vessel off the Gujarat coast, a defence spokesperson said today.

Merchant vessel 'Henry' was intercepted and detained off the Gulf of Khambat along the Gujarat coast by ICG ship 'Samudra Pavak,' the coast guard said in a release today.

The vessel was intercepted at around 12:00 hrs yesterday.

"During the initial inspection by the Coast Guard, approximately 1,500 kg of narcotics worth Rs 3,500 crore have been found onboard (ship 'Henry'). This is the biggest catch of narcotics in the present times," it said.

The intruder suspicious vessel, which was found to be registered in Panama, had eight crew members onboard and no cargo. It said it was headed to Bhavnagar for breaking at the Alang yard after being intercepted by the ICG ship in the Gulf of Khambat, which was denied by the Gujarat Maritime Board, the ICG said.

The vessel was today taken to Porbandar, and crew members were detained for interrogation in the presence of intelligence agencies, police, customs, enforcement, narcotics, and the navy, it said.

The development comes three days after the ICG was mobilised on intelligence input that an Iranian vessel Prince-II, carrying large amount of narcotics (heroin and chitta), was likely to enter Bhavnagar (Gulf of Khambat) or Jamnagar (Gulf of Kutch) in disguise, the release said.

Following this, the ICG intercepted and detained two cargo ships -- Al-Amir and Noor-E-Shabir-- on July 28 for questioning after their movement was found to be suspicious.

While they were being questioned, vessel 'Henry' was detected to be moving suspiciously in the Gulf of Khambat by ICG aircraft Dornier when it was "sanitising the sea area," the ICG said.