NICOSIA, Cyprus — A Cypriot criminal court on Friday sentenced the country's former defense minister to five years in prison over the 2011 explosion of 480 tons of seized Iranian gunpowder that killed 13 people, knocked out Cyprus' main power station and stirred up a political crisis.

The three-judge bench sentenced Costas Papacostas, 74, after finding him guilty last month of negligent manslaughter for not taking precautions that would have prevented 80 containers of gunpowder from blowing up.

The containers were left piled up in a field inside a naval base for more than two years. Authorities said that prolonged exposure to wide temperature swings made the gunpowder unstable and that the spontaneous combustion of one container triggered the disaster.

Military officials had issued warnings over the risks that such storage conditions posed. The starkest warning came a week before the fatal blast when some of the gunpowder detonated inside a container at the very top of the pile.

Three senior fire service officials — Fire Chief Andreas Nicolaou, his suspended deputy Charalambos Charalambous and Disaster Response Unit chief Andreas Loizides — were each sentenced to two years in prison on the lesser charge of causing death through a reckless act.

The gunpowder was confiscated in February 2009 from a Cypriot-flagged ship suspected of transporting the material from Iran to Palestinian militants in Gaza through Syria in breach of a United Nations ban on Iranian arms exports.

Two other defendants in the trial, former Foreign Minister Markos Kyprianou and ex-deputy National Guard Chief Savvas Argyrou, were acquitted of all charges.

The explosion prompted weeks of street protests calling for then President Dimitris Christofias' to resign over what many saw as official ineptitude. Christofias rejected a public inquiry's conclusion that he was primarily responsible for the circumstances that led to the explosion, saying his subordinates had failed to inform him about the gunpowder's storage conditions and the associated risks.

Papacostas wasn't present for the sentencing because of poor health. He continues to be treated for high blood pressure and kidney problems and had suffered a life-threatening blood clot in an artery three years ago.

The judges said they took into account Papacostas' advanced age and poor health in passing sentence.