Nokia, the world's largest mobile handset maker, has sued two Shenzhen-based phone manufacturers, Shenzhen Telsda Mobile Communication Industry Developing Co and Song Xun Da Zhong Ke Electronic Co, alleging they copied the design of its popular Nokia 7260 handset. The Finnish company said it is asking a Beijing court to force the manufacturers to stop making and selling the phones. Last year, China superceded the US as Nokia's largest market, with sales growing 28% to US$4 billion.