CAIRO — An Egyptian university student was fatally stabbed when suspected Islamic militants confronted him and his girlfriend in a park, telling them they should not be together if they are not married, security officials said Wednesday.

The slaying fueled fears that vigilante groups may be seeking to strictly enforce Islamic mores, emboldened by the election of President Mohammed Morsi, an Islamist.

Moderate Muslims along with liberal and women’s groups worry that Morsi’s presidency will eradicate Egypt’s entrenched secular traditions and change the social fabric of the mainly Muslim nation of 82 million people.

The student, 20-year-old Ahmed Hussein Eid, was attacked June 25 in the Red Sea city of Suez, east of Cairo, while he was with his girlfriend in a quiet park that is a favorite spot for romantic rendezvous, according to the officials.

It was not immediately clear what the two were doing when challenged by the three men, who arrived on a motorbike.

But the officials, citing initial testimony of the girlfriend, said the men told the couple they should not be together because they were not married and must immediately leave and go their separate ways.

A quarrel followed and one of the three men stabbed Eid in the upper thigh, near his genitals. He was hospitalized and died of his wounds a week later on Monday, according to security officials.

Suez is a stronghold of Islamists and voted overwhelmingly in support of Morsi in the June 16-17 presidential runoff against Ahmed Shafik, a career air force officer and the last prime minister to serve under Hosni Mubarak before he was ousted in an uprising last year.

The fatal stabbing took place just one day after Morsi of the fundamentalist Muslim Brotherhood group was declared the winner of the runoff.

Last week, two musicians were killed, also by suspected militants, in a Nile Delta province.

Radical Muslims take a dim view of music, considering it prohibited as a distraction from religious duties.