Piper Jaffray analyst Gene Munster has noticed a significant decline in iPhone 5S availability in the past two weeks.
He noted that in the US stock of the smartphone dropped from 27 % to just 6 % this past week.
In addition, checks of 60 Apple stores in the US have shown that the stores with at least one 5S dropped from 90 to 40 % in the past two weeks.
However, Munster believes stocks of the new iPhone may also be limited ahead of the international launches set for later this month.
Also, based on resale prices on eBay and Chinese site Taobao, Munster found that the 5S is selling at a 32% premium compared to retail prices, which is proof of strong consumer demand.
As for the low-cost 5C, the device sells at an 11 % discount of the retail price, which the analyst sees as an indicator of demand being in line with supplies.
The new iPhones will debut in more than 25 countries on October 25th.