Apple Inc has started testing a new iPhone and the next version of its iOS software, news website The Next Web reported. Following the report, the company’s shares rose as much as 4.3% on the Nasdaq stock exchange. Application developers have found in their app usage logs references to a new iPhone identifier, iPhone 6.1, running iOS 7 operating system, the website reported.

Apple’s iPhone 5 bears the identifiers “iPhone 5.1” and “iPhone 5.2” and is powered by the iOS 6 operating system.

Developer logs show that the app requests originate from an internet address on Apple’s Cupertino campus, suggesting that Apple engineers are testing compatibility for some of the popular apps, the website said. “Although OS and device data can be faked, the unique IP footprint leading back to Apple’s Cupertino campus leads us to believe this is not one of those attempts.”

Raymond James analyst Tavis McCourt expects the next version of the iconic smartphone to be called iPhone 5S and not iPhone 6.

Apple launched iPhone 5 in September and the new iPhone is likely to be released in the middle of 2013.