CAIRO march 10 (Reuters) -- Sheikh Mohamed Sayed Tantawi, the head of Egypt's most prestigious seat of Islamic learning al Azhar, died of a heart attack on Wednesday during a visit to Saudi Arabia, religious officials at al-Azhar said. He was 81.

Abdullah el-Naggar, advisor to the sheikh, told Egypt's Nile News television the death was a surprise, saying that before leaving to Saudi Arabia the sheikh had seemed in "excellent shape and health."

A member of Tantawi's office, Ashraf Hassan, told Reuters that Mohamed Wasel, Tantawi's deputy, was expected to temporarily take over leading the institution until the Egyptian president appointed a new head for the body.

Al Azhar, which runs schools, universities and other educational institutions across Egypt, receives most of its funding from the state.

When he was appointed in 1996, Tantawi was viewed as having relatively liberal views on issues such as women's rights but had been criticised by some for toeing the government's line.

In office, he opposed female circumcision as not an Islamic practice and took a stand against the full veil, or 'niqab', that completely covers the face.

Tantawi issued a religious edict last year barring the niqab in al-Azhar-run all-girl schools.

A Saudi source familiar with the situation said Tantawi died of a heart attack in the Saudi capital on Wednesday.