North Korea has deployed dozens of huge white balloons alongside its wrecked 5,000-ton-class warship to stop it from sinking further after a botched launch last week, new satellite images show.

It may be hard to fathom in today's high-tech world, but many nations used gas-filled balloons during both World Wars as active and passive defenses to keep enemy aircraft away from a target.

North Korea has sent aloft thousands of balloons with bags of trash attached since May, which have crossed the border to become a new source of tension with the neighbouring South. The balloons ...