CAIRO, Egypt — Demonstrators in Cairo demanded Tuesday that Saudi Arabia release an Egyptian doctor sentenced to 15 years in prison and 1,500 lashes after he was convicted of malpractice — reportedly after treating a Saudi princess.

His wife said she feared the punishment would kill him.

Raouf Amin el-Arabi, a doctor who has been serving the Saudi royal family for about 20 years, was convicted last year of giving a patient the wrong medication. Egyptian newspapers reported that he was accused of driving a Saudi princess “to addiction.”

He initially was sentenced to seven years in prison and 700 lashes, but when he appealed two months ago, the judge not only upheld the conviction, but more than doubled the penalty to 15 years in prison and 1,500 lashes.

Family members, friends and colleagues gathered at the headquarters of Egypt’s doctors’ union in downtown Cairo and urged Saudi King Abdullah to pardon el-Arabi.

“My children want their father to return swiftly and safely,” the doctor’s wife Fathiya el-Hindawi told the Associated Press. “I hope the king will give them back their smiles.”

She maintained her 53-year-old husband was innocent and feared he would die if given the full penalty.

“1,500 lashes is unprecedented in the history of Islam,” read one banners carried by protesters. “Who is responsible for the humiliation of our doctors abroad?” read another.

The case has drawn nationwide criticism in Egypt and local human rights groups have demanded that Egyptian President Hosni Mubarak, who maintains close ties with the Saudi royal family, intervene to free el-Arabi.

The Saudi government has refrained from comment but Egyptian newspapers report that el-Arabi was treating a female member of the royal family when he was accused of “driving a patient to addiction.” The newspapers identified the princess as one of the wives of Abdullah’s nephews.

Saudi Justice Ministry officials did not answer the phone on Tuesday to comment on the case.

Egypt’s Foreign Ministry said on Tuesday that diplomatic and political efforts are under way to resolve the problem, but warned that relations between the two countries should not be affected.

“The ministry is very much concerned with this case,” said Ahmed Rizq, a ministry official, in a statement. “However, the Saudi judicial and political system should be respected.”

Egypt’s state-owned Middle East News Agency later reported that Cairo’s ambassador to Riyadh, Mahmoud Auf, met with the powerful mayor of Riyadh, Prince Salman, to discuss “the status of Egyptian expatriates in the kingdom.”

El-Arabi is in a jail in the Red Sea port city of Jeddah and is believed to have received at least one of his weekly installments of 70 lashes so far.