Militants linked to Lebanese Shia movement Hizballah were found to be stockpiling bomb-making ingredients in London in 2015 but the case was kept "hidden from the public", according to media.



British police and the MI5 intelligence service discovered thousands of disposable ice packs containing three tons of ammonium nitrate following a tip-off from a foreign government, The Daily Telegraph reported, according to security sources.



The amount of ammonium nitrate discovered in the swoop was more than what was used for the bombs in Oklahoma City in 1995, which left 168 dead.



One man was arrested in a series of four raids in northwest London but he was "covert intelligence operation" - not aimed at seeking criminal prosecution.



The public was not informed about the swoop as it would "raise eyebrows" due to a nuclear deal being agreed with Iran shortly before.

The UK was party to the agreement, while Iran is Hibzallah's main foreign backer.



Prime Minister David Cameron and the then-Interior Minister Theresa May were informed but MPs who were debating whether to ban Hizballah in the UK were not.



Similar discoveries of ice packs used to store explosives were made in other parts of the world.



Ice packs were used for transporting the material as they looked harmless and were easier to transport, the report added.



The report added that no attack was imminent and the ammonium nitrate had not been weaponised.



The Lebanese Shia group's militant faction was already banned in the UK, but the political wing was only banned earlier this year.