Sri Lankan security forces have reported finding high-tech underwater scooters, known as 'seabobs' during a raid on a house in Amparai.
The raid, which is part of wider search operations across the island following the Easter Sunday bombings by Islamist extremists, took place on Sunday.
Security forces said they would be investigating how such sophisticated equipment was imported into the country.
The discovery fuels further questions into how the groups responsible for the bombings were able to operate and even run training camps complete with a watch tower without the knowledge of security forces, which remain deployed heavily across the North-East.
Last week security forces reported finding a camp in Omadiyamadu, a border village between Batticaloa and Polonnaruwa, which they say was used by Zahran who bombed the Shangri-La hotel.
Read more: Suicide bomber training camps found says STF
Over 250 people were killed when the suicide bombers supportive of Islamic State, detonated devices at luxury hotels and churches on Easter Sunday. Whilst the government has banned the two main organisations, National Thawheed Jammath (NTJ) and Jamathei Millathu Ibraheem (JMI), there has been increasing criticism over the government's failure to take action to prevent the attacks after it emerged India had warned Sri Lankan authorities repeatedly in the preceding weeks that such an incident was planned.
Questions have also been raised over the organisations' links with government security forces and intelligence, with reports that the intelligence authorities funded NTJ.
One Sri Lankan soldier is currently on the run after authorities said they believed he had taught the attackers how to use explosives.
St Anthony's Church, Colombo
Last week a parliamentarian claimed the former defence secretary Gotabaya Rajapaksa gave NTJ land for an office in Colombo.
Kurunegala District UNP MP Thushara Indunil however claimed that the NTJ received support from Rajapaksa, who announced that he would the running for president in elections set to be held later this year.
Indunil said the All Ceylon Jamiyathul Ulema had warned the Sri Lankan government “as early as 2014” about the emergence of the NTJ and Islamic extremists on the island. “If the former Defence Secretary was privy to this information, we ask of what he did then, knowing the threats it posed,” he said.
“He tried to divide the peaceful community of Muslims into two. He knew that it would help him in his political endeavours which is why he strengthened one group against the other. Basil Rajapaksa said that there are 200 such mosques and the defence secretary assisted in setting them up.”
Cabinet spokesperson Rajitha Senaratne said that at least four army officers were involved in organising the assassination of police officers in Batticaloa last year, and claimed dozens of NTJ were on the payroll of Sri Lankan intelligence linked to Rajapaksa.