Nicosia - A Lebanese-Canadian man was detained for a further eight days in Cyprus on Friday after five tonnes of potential bomb-making equipment was found in his home, police said.
The suspect appeared in court under heavy police guard in a hearing held behind closed doors for "national security reasons", according to police sources.
He faces possible charges of conspiracy to commit a crime and illegal possession and transfer of explosive materials, police said.
Authorities are also looking into whether the 26-year-old Lebanese-Canadian has possible links with the military wing of the Shiite militant group Hezbollah.
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Police asked the court for more time to complete their investigation, which also involves cooperation with international law enforcement agencies.
The man was arrested last month in the coastal resort city of Larnaca in possession of what authorities said at the time was two tonnes of ammonium nitrate, a fertiliser that when mixed with other substances can be used to make explosives.
Police said closer inspection showed the man's home to contain more than five tonnes of the material.
Police spokesman Andreas Angelides told state radio Friday that an operation was underway to remove the chemicals from the property.
The man arrived in Cyprus on May 21 for what he described as a holiday. He was arrested in a Larnaca suburb on May 27 following a surveillance operation.
Local media reports said authorities had not ruled out that the suspect was planning an attack on Israeli targets on the Mediterranean resort island, which attracts thousands of visitors from nearby Israel each year.
In 2013, a Cypriot court convicted a Lebanese-born Swedish man who admitted he was a Hezbollah member. He received a four-year jail term after being found guilty of targeting Israelis on the island.