The Saudi Arabian government has sentenced 15 people to death and jailed many more over an alleged spy ring that handed secret documents to arch-enemy Iran.

A court in the capital of Riyadh also gave prison terms ranging from six months to 25 years, and acquitted two, over a three-year case that has involved 30 Saudis, one Iranian and one Afghan.

The gang allegedly attempted to recruit people working in state agencies and hack into computers for sensitive information.

Almost all of the defendants are Shia Muslims, in what is a Sunni-dominated country, and are from the oil rich Eastern province where street protests calling for democratic reform have bubbled up since the Arab Spring.

Anger reached fever pitch in this region, when in January, leading celric and vocal regime critic Sheikh Nimr al-Nimr was executed for alleged involvement in the killing of policemen.

The publicity has swept aside headlines surrounding the Saudis involvement in the Yemen civil war, which has killed more than 10,000 civilians.

During times of low oil prices, Saudi prince Mohammed bin Salman has slashed capital spending by 71 per cent and ministers' pay by 20 per cent.

Earlier this year, Saudi Arabian officials said they would behead a disabled man for taking part in protests.

The death penalties for the 15 alleged spies are open to appeal.

Relations between Saudia Arabia and Iran soured after the latter's 1979 Shia revolution.