By Soham Chatterjee (Reuters) - Apple Inc said it sold more than 10 million iPhones in the first weekend after its new models went on sale on Friday, underscoring strong demand for phones with larger displays. Chief Executive Tim Cook said the company could have sold even more iPhone 6 and iPhone 6 Plus models if supplies had been available. Analysts had estimated first-weekend sales of up to 10 million iPhones, after Apple booked record pre-orders of 4 million on Sept. 12, the day pre-orders opened. Apple's shares were little changed at $100.98 in afternoon trading on the Nasdaq on Monday. The company's first-quarter revenue is likely to be 9 percent higher than Wall Street estimates, based on reported sales and projected demand for the new iPhones, Piper Jaffray & Co analyst Gene Munster wrote in a note. Munster said he expected earnings per share to be 12 percent higher than estimates. "Despite the supply chain constraints around the iPhone 6 Plus and tightness around certain models of the iPhone 6, we believe (Monday's) strong print demonstrates that Apple executed extremely well in the face of severe supply constraints," Cantor Fitzgerald analyst Brian White wrote in a note. First-day pre-orders for the new phones, which went on sale in 10 countries, far surpassed the 2 million recorded for the iPhone 5 model two years ago. "While our team managed the manufacturing ramp better than ever before, we could have sold many more iPhones with greater supply and we are working hard to fill orders as quickly as possible," Cook said in a statement. Apple sold 9 million iPhone 5S and 5C models last year in 11 countries, including China, in the first weekend they were available. Sales of the latest models in China, the world's largest smartphone market, have been delayed by regulatory issues. Lured by the prospect of profit from smuggling the new iPhones into China, opportunists joined the scores of fans outside Apple stores to buy the devices. Police in New Haven, Connecticut said fights broke out among customers believed to be rival groups of Chinese men and women who were apparently trying to buy as many iPhones as possible to resell them at a significant mark-up in China. Three people were arrested, one of whom suffered a small cut to his forehead and was treated in hospital. "Store managers have phoned several times to report fights and ill-behaved line waiters," the New Haven Police Department said in a statement. Apple said last week that many U.S. customers would have to wait until next month for their new iPhones due to strong demand. The company routinely faces iPhone supply constraints, particularly in years that involve a re-design. The new iPhones will be available in 20 more countries on Sept. 26, Apple said. The company sold 5 million iPhone 5 handsets, 4 million iPhone 4S models and 1.7 million iPhone 4 units during the first weekend. The shipment levels of iPhone 6 and iPhone 6 Plus are positive, given that the new models are not initially available in China, Stifel Nicolaus & Co analyst Aaron Rakers wrote in a note. Rakers noted that the latest models would be available in 115 countries by the end of this year compared with 100 for iPhone 5S and 5C. (Additional reporting by Scott Malone; Editing by Ted Kerr and Kirti Pandey)