CAIRO (REUTERS) - Al-Azhar, the centre of Islamic learning in Egypt, on Thursday condemned the killings of three young Muslims by a gunman in the United States as a "terrorist and racist" act.

A man who had posted anti-religious messages on Facebook and quarrelled with neighbours has been charged with the shootings.

Muslim activists in the United States and around the world have demanded authorities investigate a possible motive of religious hatred.

Police said on Wednesday the case involved a dispute over parking and possibly a hate crime.

Craig Stephen Hicks, 46, a full-time paralegal student from Chapel Hill, was charged with first-degree murder in Tuesday's killings 3km from the University of North Carolina campus.

"Al-Azhar expresses its deep shock and concern at this cowardly terrorist act, which indicates that terrorism has no nationality or religion," said a statement issued by the 1,000-year-old seat of religious learning, respected by Muslims around the world.

The victims were newlyweds Deah Shaddy Barakat, 23, a University of North Carolina dental student, his wife Yusor Mohammad, 21, and Yusor's sister, Razan Mohammad Abu-Salha, 19.

A judge on Wednesday ordered Hicks held without bail pending a March 4 probable cause hearing.

Al-Azhar urged US authorities to bring the perpetrators to justice "in order to prevent its recurrence which may lead to widening the gap between the east and the west".

Some Muslims in Arab states have accused the Western media and governments of paying too little attention to the killings, in contrast with the blanket coverage of the attack on the Paris offices of Charlie Hebdo, a satirical magazine known for lampooning radical Islam, in January.