The Australian Stock Exchange is back online after trading was halted for four hours on Thursday due to a technical glitch. Trading resumed at 2 p.m. after the market stopped at 10:05 a.m.

Following the resumption of trading, the S&P/ASX 200 index increased by almost 2 per cent to 4,326. The ASX said trades that were placed under review because of the glitch would now stand and started to be processed from 1:40 p.m.

About $5 billion worth of trades were missed during the morning trading, but the bulk was put back on resumption of the ASX.

The shares jump was mainly due to agreement by European leaders with private banks to voluntarily reduce by 50 per cent Greek debts to help address the euro zone's debt crisis.

Despite the resumption of trading, the ASX has not yet discovered what kind of technical fault hit its trading system which caused all markets to be placed on "enquire." ASX General Manager for Media and Communications Matthew Gibbs said the glitch is being investigated.

Prior to the glitch, 6,700 trades were made. Gibbs said all these trades would be reassessed.

The outage came just two trading days away from the opening of rival market operator Chi-X which is slated to go live Monday. Chi-X will break ASX's effective monopoly on Australian share trading after it secured a licence more than three years after applying for one.

Chi-X Australia Chief Executive Officer Peter Fowler said that should a similar technical glitch hit Chi-X similar to what happened to the ASX, it could still continue with trading because of built-in redundancies in its trading system.