"The Kingdom of Saudi Arabia, its people and government stood and stands by today with its brothers in Egypt against terrorism," he claimed.

"I call on the honest men of Egypt and the Arab and Muslim nations ... to stand as one man and with one heart in the face of attempts to destabilize a country that is at the forefront of Arab and Muslim history," he added.

Saudi Arabia was a close ally of former president Hosni Mubarak and has historically had a difficult relationship with the Muslim Brotherhood.

It pledged $5 billion in aid to Egypt after Mohammed Morsi of the Brotherhood was ousted from the presidency last month.

Most Arab leaders tacitly support Egypt's deadly crackdown on the Muslim Brotherhood, fearing the group's growing regional influence since the Arab Spring threatens their own power, analyst say.

Khattar Abou Diab, a professor at University of Paris-Sud, said all the Persian Gulf monarchies, in particular Saudi Arabi, fear that the Muslim Brotherhood revolution will be exported to them," said.

"For that reason, they are hoping for a return to the classic situation of a strong power in Egypt, a pivotal country in the Arab world," he said.

But only Qatar, a Brotherhood patron, and Tunisia, whose ruling Ennahda party is affiliated with the movement, reportedly condemned the assault.

Egypt's army, directly or indirectly in power since 1952, ousted the Brotherhood's democratically elected Mohamed Morsi as president in a July 3 coup and installed an interim civilian government in its place.

Morsi's supporters set up protest camps in Cairo and promised to stay put until the former leader, now in custody, was reinstated.

The government ordered them to disperse and, after a number of delays, police backed by troops stormed the camps on Wednesday.

The death toll from ensuing clashes, in the capital and across Egypt, has reached over 600 people.