The phones went on sale on 19 September, after Apple unveiled the new models at its Cupertino event earlier this month.
This is the first time Apple has introduced a larger-sized model with the iPhone 6 Plus, an acknowledgement that consumers increasingly prefer bigger phones such as Samsung's Galaxy series.
Analysts greeted the 10 million figure as a "positive surprise", given limited supplies of the iPhone 6 Plus and earlier estimates of muted sales.
Despite an intense media focus on whether Apple can maintain its shine, CCS Insight analyst Ben Wood said the company remains a "darling" in the eyes of consumers.
Anyone who was wondering whether Apple’s brand lustre was fading has been given the strongest signal to date that it is as strong as ever
"There was clear pent up demand for the new iPhones but the first weekend of sales further underline the strength of Apple’s current position," he told Marketing.
"Anyone who was wondering whether Apple’s brand lustre was fading has been given the strongest signal to date that its dominant status in the smartphone market is as strong as ever," he added. "Rivals will be looking at this first weekend’s sales in a state of shock and awe."
But commenters also pointed out that first weekend sales figures tend to be "meaningless", since they only reflect Apple's supply, rather than consumer demand. As such, that 10 million figure indicates how fast Apple can produce its new devices, rather than how many consumers will eventually buy them.
"We caution investors that first weekend sales for iPhones is a meaningless figure since it really only represents Apple’s supply," wrote Barclay's analyst Ben Reitzer. "Demand is clearly there for the phones – in the 10s of millions right now and significant demand will likely spill out of September into future months."
CEO Tim Cook noted that the company could have sold more iPhone models had there been more supply.
Apple set its previous first weekend sales record with last year's iPhone 5S and cheaper iPhone 5C, at nine million combined sales.