briefly unavailable; cause not immediately clear

Nicholas Kamm | AFP | Getty Images's website was widely unavailable for approximately 30 minutes Monday afternoon, but the cause was not immediately clear.

Calls to the Internet retailing behemoth have not yet been returned, and there was no mention of the outage on Amazon's official Twitter feed.

Last week The New York Times' website was unavailable for a couple hours, from late morning until early afternoon, which the company said appeared to be the result of an "internal issue."

A group calling itself the Syrian Electronic Army last Thursday launched a cyber-attack that affected the websites of The Washington Post, Time and CNN, among others.

This story is developing. Please check back for further updates.

Click here for the latest on the markets.