The 16 crewmen on board were seized by North Korean forces earlier this month. A ransom worth around £60,000 is being demanded.
One European diplomat told me last week that during his conversations with Chinese officials the turn of phrase and tone of conversation when North Korea was raised, gave him the clear impression that all was not well between Beijing and Pyongyang.
The launching of four short range missiles over the weekend can only add to the displeasure already being expressed privately by China's leaders.
North Korea has always been a stubborn thorn in China's side, but North Korean leaders have always known that they can push China a long way because China would never allow a political ally, a neighbour and a buffer zone between Chinese borders and US troops to collapse.