North Korea fired two short-range missiles, fuelling tensions sparked by its nuclear standoff, as a US team began talks in China on ways to make UN sanctions bite against Pyongyang. The missiles were launched in the early evening from a base near the eastern port of Wonsan, South Korea's defence ministry said. They appear to be ground-to-ship missiles, which were launched into the East Sea (Sea of Japan), a spokesman told. The North has responded angrily to United Nations sanctions imposed following its long-range rocket launch on April 5 and a May 25 nuclear test, and vowed to bolster its defences. In the days after its atomic test -- the second since 2006 -- Pyongyang had fired a total of six short-range missiles and renounced the truce in force on the Korean peninsula. In response to a UN resolution on June 12 tightening curbs on its missile and atomic activities, it vowed to build more nuclear bombs.Seoul's defence ministry refused to confirm a Yonhap news agency report that the North Thursday fired KN-01 missiles with a range of up to 160 km. The South rejects the North's demand for huge pay rises and rent increases at Kaesong, and demands freedom for a South Korean worker who has been held for more than 90 days. The North alleges the man slandered its political system and tried to incite a local woman worker to defect. It refuses to grant access to him.