Chinese President Hu Jintao, Turkmen President Gurbanguly Berdymukhamedov, Kazakh President Nursultan Nazarbayev and Uzbek President Islam Karimov turn on the flow of natural gas together in the gas plant on the right bank of the Amu Darya River, Turkmenistan, on Dec. 14, 2009. The four leader attended the inauguration ceremony of the China-Central Asia natural gas pipeline here on Monday.[Xinhua]