Associated Press
Egyptian boys hold posters of Ahmed Hussein Eid, who was fatally stabbed by three bearded men as his girlfriend looked on, during his funeral procession in the city of Suez, Egypt, on Wednesday.

CAIRO — Three bearded men approached a university student and his girlfriend during a romantic rendezvous in a park and ordered them to separate because they weren't married, according to security officials. An argument broke out, ending with one of the men fatally stabbing the student.

The June 25 attack has alarmed Egyptians concerned that with an Islamist president in office, vigilante groups are feeling emboldened to enforce strict Islamic mores on the streets.

Islamists, including members of one-time violent groups, were empowered after last year's ouster of Hosni Mubarak's secular regime by a popular uprising. They formed political parties and won about 70 percent of parliament seats in elections held some six months ago, although a court dissolved the legislature.

Moderate Muslims along with liberal and women's groups now worry that Mohammed Morsi's presidency will eradicate what is left of Egypt's secular traditions and change the social fabric of the mainly Muslim nation of 82 million people.

Some activists say Islamists already are flexing their muscles in areas outside Cairo and other main cities, taking advantage of the absence of civil society groups and tenuous security in the areas.

They cite reports of efforts to persuade drivers of communal taxis, mostly minibuses that can seat up to 16, to segregate women and men passengers. In some instances, women's hairdressing salons were told to get rid of male employees or threatened with closure.

"If Islamists are to try and take over the streets and enforce their version of Islam, they will do it in rural areas, at least initially," said Yara Sallam from Nazra, a women's rights group.

The security officials said there was no concrete evidence linking the June 25 killing to radical Islamic groups in Egypt, but it still has stoked fears.

Islamist groups, including Morsi's Muslim Brotherhood and the ultraconservative Salafis, denied any link to the murders.

Rights groups say they have sent teams to investigate the Suez killing and establish whether Islamists were behind the attacks.

On the same day, two musicians, who were brothers, were murdered as they were traveling home after performing at a wedding in the Nile Delta province of Sharqiyah, officials said. Radical Muslims consider music "haram" or prohibited, as a distraction from religious duties.

Two ultraconservative Salafi Muslims were arrested, but officials said it was not clear if the killings were religiously motivated.

Nonetheless, thousands of residents of Abu Kibeer, the victims' hometown, protested the killings, cutting off roads and disrupting train services by sitting on the rails. They also destroyed the local offices of a charity they suspected the culprits belonged to and torched the home of one suspect.

Some activists believe that the Brotherhood is at least quietly condoning nonviolent activity designed to bring the country more in alignment with Islam's teachings — a founding goal of the 84-year-old fundamentalist movement.

About 100 activists, political parties and non-governmental groups have issued a statement calling on Morsi to protect women against what it said was growing incidents of harassment, particularly against those not wearing the Muslim veil.