Somali pirates to periods ranging from four to seven years for their role in abducting two South Africans off a yacht in the Seychelles last year."During the attack on the [yacht] Choizil, extreme violence was used," said Judge Jacco Janssen at a hearing held in the southern Dutch port city of Rotterdam on Friday.
"The crew thought their last hour had arrived," he added.
Omar Ali Abdallah, 24, was sentenced to seven years, while Sadag Ali Ibrahim, 20, received a six-year jail term for the attack on the South African yacht.
The three other men, including the pirate group's 23-year-old leader, were sentenced to between four-and-a-half and five-and-a-half years for complicity to piracy.
The five accused pirates were part of a group of 20 people picked up by a Dutch navy supply ship off the Somali coast in late November last year, and were transferred to the Netherlands on December 5.
Fifteen others were released due to a lack of evidence.
Piracy on the rise
"The number of piracy attacks and hijacking of ships along the Somali coastline has increased substantially over the last few years," Janssen said, adding the route along the coast was one of the busiest in the world.
"The free movement of freight, raw materials and fuels are more and more in peril. This could have global economic implications," he said.
"Pirates have also notably become more professional, more violent and more reassured in their deeds. The motive is clear: it brings in enormous amounts of money."
The couple named by South African media as Bruno Pelizzari and Debbie Calitz are still being held by Somali pirates at an unknown location, with a $10m ransom being asked for their release, Dutch prosecutors said.
A statement on Friday from the Rotterdam court said the judges dismissed arguments that the suspects were driven to piracy by poverty and famine.
Two decades of anarchy have allowed pirates to flourish off Somalia's coasts.
Some of the captured pirates have been extradited to other countries for prosecution.