North Korea has test-fired two short-range missiles off its east coast, South Korea's defence ministry spokesman has said. The launch of the surface-to-ship missiles could further stoke tensions already high after the North's May 25 nuclear test. Washington said earlier this week it had tightened its crackdown on firms linked to the North's proliferation of missiles, which is a major source of cash for the destitute state. Philip Goldberg, the US envoy who co-ordinates sanctions against the North, went to China to enlist Beijing's help in getting tough with the hermit state. China is the North's biggest benefactor whose co-operation could determine the success of any sanctions against the regime, analysts said. China is sending its envoy to the six-country talks - aimed at ending the North Korea's atomic ambitions - to South Korea, Japan, Russia and the US. North Korea, the final party in the talks, is not on the itinerary. "China has consistently advocated dialogue and consultation, and achieving denuclearisation of the Korean peninsula through the six-party talks process," foreign ministry spokesman Qin Gang told a news briefing. South Korean Foreign Minister Yu Myung-hwan said he is seeking a meeting of the foreign ministers of the six countries including the North on July 23 in Thailand. Analysts said the North's military grandstanding is probably related to moves by its leadership to begin readying leader Kim Jong-il's youngest son as a future heir by consolidating the 67-year-old leader's power base.