Children now? Pirate Content...
Somali pirates 'seize Danish children' in Indian Ocean
Denmark's foreign ministry said the children were aged between 12 and 16, and that two Danish crew members were also captured during the attack.
Pirates seized the boat on 24 February and were said to be heading to Somalia.
Piracy is a highly lucrative trade in Somalia, where gangs can often demand millions of dollars in ransoms.
As of last week, the EU's anti-piracy naval force said pirates were holding a total of 31 vessels, and 688 hostages.
Many of the vessels they target are cargo ships sailing near the Gulf of Aden - one of the world's busiest shipping lanes.
The foreign ministry told the AP news agency that the ship sent a distress signal on Thursday: "It has now been confirmed that the sailboat was hijacked by pirates."
The Danes are be the second group of non-commercial sailors seized by pirates in recent weeks.
A group of Americans was seized earlier in February, and four of them were killed as the US Navy tried to rescue them.
US forces say the pirates shot them.
Analysts say the piracy industry is becoming increasingly lucrative - Somali gangs recently hijacked a tanker with $200m (£136m) worth of crude oil on board.
International naval forces patrolling the area are becoming more willing to send in commando teams to free hostages.
But the pirates also appear to be responding with increasing violence - two Philippine sailors were murdered last month by pirates angered at an attempted rescue.
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You can't steer a boat that isn't moving? Just like a life - P. Lutus