The US is again using its whistleblower programme to keep the shipping industry in line.

This time, the US State Department's Rewards for Justice scheme is offering up to $5m for information disrupting North Korea's alleged sanctions-violating activities, which it says finance its nuclear weapons programme.

The incentive comes as the US accuses China of helping Pyongyang to violate international sanctions, including sending ships laden with prohibited goods to North Korea 555 times in the past year, according to Reuters.