"Saudi Arabia's highest religious authority has issued a stern rebuke to women who appeared at a conference unveiled in the presence of men.
Grand Mufti Sheikh Abdul-Aziz al-Sheikh said the women's behaviour was shameful and warned of "grave consequences".
His remarks came after the country's leading businesswoman made a speech without a headscarf at an economic forum in the Red Sea port of Jeddah.
Lubna al-Olayan used the speech to call for female empowerment in the kingdom.
She said it was essential for Saudi Arabia's economic wellbeing for the potential of the country's female workforce to be unlocked.
"Without real change there can be no real progress," she said. "If we in Saudi Arabia want to progress we have no choice but to embrace change."
Her words were echoed by other women delegates.
Resistance to change
The men and women at the conference were separated by a screen, but the women were able to mix with the men in their section - something normally prohibited in Saudi Arabia.
The next day, Saudi newspapers showed pictures of the unveiled women and several editorials spoke of their behaviour as the beginning of the liberation of Saudi women.
But the grand mufti's statement made clear that the religious authorities would fight any change.
"I severely condemn this matter and warn of grave consequences," he said.
"What is even more painful is that such outrageous behaviour should have happened in Saudi Arabia, the land of the two holy shrines (Mecca and Medina)."
The remarks came as the Saudi authorities moved to introduce limited reforms.
Correspondents say the problem now is to continue to keep a lid on the cauldron of competing interests in the Islamic establishment and an increasingly impatient lobby demanding reform without the pressure boiling over into serious unrest. "