China's 3rd Flotilla arrived in the waters of the Gulf of Aden off Somalia to carry out escort mission against pirates. The second flotilla, DDG-167 Shenzhen (back) and FFG-570 Huangshan, will be replaced by FFG-529 Zhoushan （front）and FFG-530 Xuzhou, which carry two helicopters and a Special Forces unit. [Xinhua]