Cyprus has barred a ship carrying military equipment from leaving until inspectors confirm its cargo does not breach UN and EU arms embargos.
Commerce Minister Antonis Paschalides told Cyprus Radio there was "prohibited material" on board the Santiago, such as explosives and military equipment.
The manifest of the vessel says it was sailing to Sudan and Singapore.
The EU bans arms shipments to Sudan, while there is a UN embargo on armed groups in the nation's Darfur region.
Two rounds of north-south civil war since the 1960s have cost the lives of about 1.5 million people.
Meanwhile, a continuing conflict in Darfur has driven more than 2.6 million people from their homes and killed 300,000, according to the UN.
On Tuesday, the Cypriot authorities said an Antigua and Barbuda-flagged cargo ship had been anchored off the island's southern port of Limassol since 11 June, when it was inspected while refuelling.
"There is material [on board] which is considered prohibited from leaving Cyprus right now," Mr Paschalides told Cyprus Radio. "When we speak of prohibited material it means explosives or military material.
"I cannot specify right now what material it is, whether it is tanks, not tanks or other things, but there is definitely military material which comes under export control," he added, responding to local media reports.
The minister said the vessel's papers suggested it had sailed from Norway and had passed through the German port of Hamburg and through Spain.
Police said they were checking the authenticity of the documents.
The local newspaper Phileleftheros, which broke the story, reported that the ship had been held after a tip-off from the US authorities.
The US embassy in Nicosia said Washington was not involved.
In 2009, Cyprus intercepted a ship heading to Syria from Iran carrying weapons-related material and confiscated its cargo.
The authorities said at the time that the cargo was in "clear" breach of UN sanctions banning arms exports from Iran.