Cairo: Saudi Arabia's monarch will announce a government reshuffle, an anti-corruption drive and a promise to increase food subsidies to combat rising prices in his first address to his nation since unrest began sweeping the Arab world, diplomats have said.

King Abdullah Bin Abdul Aziz's speech is expected after Friday midday prayers.

The rare speech by the country's 86-year-old monarch comes after a several small demonstrations in the kingdom.

Though only dozens of people have participated, it appears the monarchy is worried the protests could escalate into more intense gatherings, inspired by the unrest sweeping the Arab world.

The diplomats said the king will replace the ministers of defence, higher education and religious affairs. The defence minister is ailing, while intellectuals have criticised the minister of higher education for dumping billions on expensive projects that they said produced few results.

The diplomats said the king would not replace the head of the all-important oil ministry. The Saudi-based diplomats requested anonymity because the royal court had not made details of the king's speech public.

Just as important for Saudi residents, they said the king will promise to try resolve the country's corruption and persistent high unemployment. Many Saudis have seen little benefit from their country's oil wealth.

Although the new changes will not loosen the tribal monarchy's tight hold on power, the king will promise moves that will strengthen dialogue, they said.

The king will announce a new institution to fight corruption, they said, but had no further details. He will increase subsidies for increasing food basics, they said, and he will also deal with Saudi residents who lost their savings in a 2006 stock market crash, but it was not immediately clear what kind of action he would take.

The king will cancel some fees for government services and announce development projects in health and education, the diplomats said.