Two Australian fighter jets bombed and sank an impounded North Korean cargo ship on Thursday in what Foreign Minister Alexander Downer said was a strong message to Pyongyang about its involvement in drug running, according to Reuters. The 4,000-tonne ship the Pong Su had been impounded since 2003, when it led the Australian navy on a 1,100 km (680 mile) chase off the southeastern coast after being spotted unloading part of a 150 kg (330 lb) shipment of heroin at a secluded beach. The ship came to a spectacular end on Thursday when two Royal Australian Air Force frontline F-111 jet bombers fired missiles into the vessel during target practice at a secret location offshore. "It is appropriate that we publicly demonstrate our outrage at what has happened by sinking this ship," Downer said. Four Pong Su crew members pleaded guilty to drug smuggling charges, with two sentenced to 23 and 22 years in jail and two yet to be sentenced. But the ship's captain and three officers were sent back to North Korea earlier this month after being found not guilty of aiding the drug operation. Downer said the heroin, worth about A$160 million ($115 million), would have provided four million hits of heroin on Australian streets. He said Australia remained concerned that the North Korean government was involved in the smuggling operation to help support its failing economy - accusations rejected by Pyongyang. Downer said Australia was determined to publicly sink the ship as a message to North Korea and other countries that they must make sure they do not support drug trafficking. "It is very important that the North Korean government makes sure, in future, that none of its ships are engaged in these sorts of activities," Downer told reporters in Adelaide.