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HONG KONG — Xiaomi, the fast-rising Chinese smartphone maker, has mustered a new $1.1 billion war chest in its latest round of fund-raising, the company’s founder and chief executive said on Monday.

The round valued Xiaomi at $45 billion, Lei Jun, the founder, said in a post on his verified account on Weibo, China’s Twitter-like messaging service. At that level, Xiaomi, which last summer claimed the No. 1 position in China’s smartphone market — the world’s largest — is now worth much more than household technology company names like Sony or Nokia, and nearly as much as Yahoo‘s current market value.

Xiaomi, founded in 2010, has overtaken both Samsung and Apple in China by offering inexpensive, high-quality phones through clever online marketing campaigns that appeal to China’s growing ranks of young and affluent consumers. Around 500 million smartphones are expected to be sold in China in 2015, more than three times as many as will be sold in the United States, according to the research firm IDC.

Xiaomi’s latest round of fund-raising includes capital from All-Stars Investment, Mr. Lei said in his post, an investment fund run by Richard Ji, a former Morgan Stanley analyst.

Other investors include GIC, Singapore’s sovereign investment corporation; DST Global, a fund run by the Russian billionaire Yuri Milner and an early investor in Facebook; Hopu Investment Management, one of China’s biggest private equity groups; and Yunfeng Capital, another Chinese private equity company set up by Jack Ma, the founder of the Alibaba Group, the Chinese e-commerce giant.

In China, Xiaomi has been compared to Apple — and not always in a flattering way. It has been accused by critics and even some faithful Chinese customers of copying Apple, from the design of its phones to its sleek marketing events for new products.

But the start-up smartphone maker’s fast growth, competitive pricing and innovative marketing have struck a chord with Chinese consumers. The company hopes this approach will translate into success in overseas markets, too. Mr. Lei and his co-founders, who include the former Google executive Lin Bin, Xiaomi’s president, are considering expansion into large developing markets like India and Brazil.

But challenges abound. For example, Xiaomi lacks a large patent portfolio of its own and was temporarily blocked this month from India because of a patent compliant filed by Ericsson, the Swedish maker of telecommunications equipment.

Domestic rivals, too, are a factor. Already, competitors like Huawei and ZTE are following Xiaomi’s strategy by selling some models primarily online. And other Chinese start-ups are trying to undercut Xiaomi by selling high-quality phones at rock-bottom prices.

Xiaomi, a privately held company, doesn’t disclose its financial performance. Previous fund-raising rounds valued the company at about $4 billion in June 2012 and $10 billion in the summer of 2013.

But at $45 billion, the latest, rapidly spiraling valuation of Xiaomi is likely to raise expectations among investors for an initial public offering, which investment bankers are already maneuvering to help manage. Company insiders have said Xiaomi is probably still years away from an I.P.O.

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