A UPS truck parked outside a San Francisco Apple store has been robbed of more than 300 iPhone Xs, just one day before the flagship's release.

In broad daylight, at around 11.15am local time, three hooded men managed to rob 313 iPhones at a total value of $370,000 (£283,000).

CNET is reporting that a janitor saw the suspects unloading boxes from the UPS truck into a Dodge van. "It's suspicious they were able to get that large a haul on that day," he said. The UPS driver reportedly locked the cargo area before leaving the Stonestown Galleria mall.

The San Francisco store opens about eight hours later than stores in the UK because of the time difference. Buyers at the Stonestown Galleria Mall face a nervous wait to see if the stolen stock will affect quantities available at launch, or if Apple is planning to replace the missing 313 iPhone Xs.

Demand locally for the iPhone X has been high, with pre-orders for the device already stretching into December. Hundreds of people lined up outside the Regent Street and Covent Garden stores for the 8am opening on 3 November.

According to data from Slice Intelligence, iPhone X pre-orders have surpassed the iPhone 6, the former peak of iPhone reservations. The majority of buyers are switching from an iPhone 7 Plus (33%) and iPhone 7 (18%). Just under 5% are moving across from a Samsung or Google phone.

The data also shows that pre-orders for the iPhone 8 and 8 Plus suffered because of anticipation for the iPhone X. The two phones combined received half as many pre-orders as the iPhone X.

IBTimes UK has reached out to Apple for comment.