Saudi state oil company Saudi Aramco said on Tuesday it had shut some of its computers for an upgrade and denied it had suffered a cyber attack similar to one it experienced last year.

Posts earlier on the Twitter social network said some or all of Aramco's computers were down, possibly because of a cyber attack.

"Saudi Aramco confirms its electronic network is completely safe and speculations of an electronic breach are completely untrue and we point out that the shutdown that took place is a temporary shutdown of a limited number of personal computers at the company that was the result of an update of some electronic applications of the network," the company said.

In August 2012, Aramco suffered an attack on 30,000 computers, which Saudi Arabia said was aimed at stopping oil and gas output of the world's biggest crude exporter. It did not say who organised the attack, which had no impact on production. - Reuters