Google has revealed re-routed traffic is to blame for an outage that left its main search engine and news functions unavailable to millions of users yesterday.

The company reported that the outage, which started just before 3pm, caused about 14 percent of Google users to face slow service or interruptions. The problem also affected Gmail, Google Apps and Google Reader.

"We've been working hard to make our services ultrafast and 'always on', so it's especially embarrassing when a glitch like this one happens," said Urs Hoelzle, Google senior vice president of Operations in a blog.

"We're very sorry that it happened, and you can be sure that we'll be working even harder to make sure that a similar problem won't happen again."

Hoelzle explained that the system error directed some of their web traffic through Asia, creating the hangups and interruptions.

"Imagine if you were trying to fly from New York to San Francisco, but your plane was routed through an airport in Asia," he said.

"And a bunch of other planes were sent that way too, so your flight was backed up and your journey took much longer than expected. That's basically what happened to some of our users today."

"Outages like this are highly publicised today, users are vocal and the news spreads like wildfire," said Dan Olds, an analyst with the Gabriel Consulting Group.

"It will have an impact on Google, as it makes their services look less than reliable. While the problem was very short-lived, just a few hours in most cases, the hue and cry from users and the tech media echo chamber make it sound like it was much worse."

Caroline Dangson, an analyst for IDC, said today's outage made her glad she's not dependent on Google Apps for her work.

"When we look at businesses dependent on Google Analytics or Gmail, they can't afford to have Google crash on them," she added.

"It's bad for business. The enterprise will start to consider using something that's always on - more reliable. It's a problem when you have this kind of hiccup system-wide and you're not seen as dependable."

Bob Dowson, director at website monitoring and load testing specialist, NCC Group said: "This is not the first time that Google has suffered availability problems, and the latest issues will undoubtedly impact negatively on user confidence".

"As the most popular search engine on the web by some distance, even this minor outage has had a widespread impact. This unexpected downtime, while damaging, is unlikely to stop most people from visiting the website and using Google services - there is not another search engine of its quality."