Bloomberg terminals used by subscribers to make trades using real-time developments in business and finance were struck by a "global network problem" for several hours Friday, the company said.

After users in financial centres around the world flocked to Twitter to complain of the unexpected outage of terminals, Bloomberg technicians began repair operations that started bringing some blanked terminals back on line at around 0945 GMT.

"Significant but not all parts of our network experienced a disruption today," a Bloomberg spokesman said to AFP in an message emailed to AFP at around 1145 GMT.

"We have restored service to most customers and are making progress in bringing all parts of the network back online. We apologise to our customers."

Despite that improving access situation, Bloomberg still appeared unable to pinpoint the exact cause of the blackout that began hours before.

It is little wonder that business and finance professionals in financial capitals like London, Singapore and New York noticed the Bloomberg breakdown immediately -- and began expressing their concern over it on social media posts just as fast.

Bloomberg terminals feed movements of global equity, commodity, foreign exchange and derivative markets to worldwide subscribers. Many of those are themselves traders and strategists in the global financial sector, and consider the service an essential tool.

When their screens went blank, many of those professionals were left without information they require to do business -- including the terminal's application many use to make trades.

"(The outage) is really disruptive for everyone," said London-based Natixis bond strategist Rene Defossez, who is responsible for working daily forecast and advisory models.

"Those function using Bloomberg data, which makes this a real problem."


'Waiting to connect'

Breakdowns in the Bloomberg system are extremely rare, and many finance professionals found themselves stranded and stunned when their screens went blank.

Trading volumes in Europe were down due to the breakdown, analysts said, and the British government was forced to postpone an emission of Treasury bills as it uses Bloomberg's bidding system.

Bloomberg is not the only provider of real-time financial information, with rivals like Thomson-Reuters offering alternative data feeds.

Yet Bloomberg has become the leader and default resource for a majority of finance professionals.

"Those who work with American investors prefer Bloomberg," says Xavier de Villepion, a stock broker with HPC in Paris.

As a result of Bloomberg's dominance, said Alastair McCaig, a London-based market analyst for online brokerage IG, the effects of its terminals going blank Friday were apparent right away.

"Bloomberg, normally a byword for dependability, has been hit with technical issues this morning," McCaig said. "As a consequence trading volumes are a little lower in the early session."

Friday's outage even sent terminals within the Bloomberg group offline, with nothing alighting many screens but the frozen "waiting to connect" message.

"Unfortunately this is a global issue. I also am locked out of my terminal," said a Bloomberg employee contacted by AFP.