At least one person has been killed and 28 others injured in the Egyptian city of Port Said in overnight clashes involving supporters of ousted President Mohamed Morsi, state news agency MENA has reported.

Witnesses and MENA said on Sunday that Morsi supporters had opened fire during a funeral of a fellow loyalist, but the former president's Muslim Brotherhood group denied the claims.

"Mourners at the funeral of a young supporter of Morsi... opened fire on the Saint George church during the funeral and burned a police car in front of it," Port Said resident Al-Tabei Faruq told the AFP news agency.

But Urfa Abu Salmiya, a spokesman for the Brotherhood's Freedom and Justice Party, denied that Morsi supporters started the clashes. "Some youths attacked mourners at the funeral," he said.

Mohamed Alaa al-Din, 16-year-old and a member of the Ultras Green eagles - fans of the Port Said football club - died from a gun shot wound in the back, according to the deputy health minister in Port Said, Helmy al-Efny.

'Shelter in mosque'

Sources told Al Jazeera that Morsi supporters took shelter in Al-Tawhid mosque in the city, the location of their their sit-in that was surrounded by local residents.

At least two shops owned by Muslim Brotherhood members and supporters were burnt by local residents.

Ultras Ahlawy fans, supporting the prominent Ahly football club, were said to have been involved alongside the local residents who fought with Morsi supporters.

The fighting in Port Said came after more than 70 people were killed in clashes between security forces and Morsi supporters in Cairo's Nasr City in the early hours of Saturday.

Witnesses accused security forces of using live fire, but the interior ministry said only tear gas was fired at demonstrators.

Morsi camp said more than 100 people were killed, while the health ministry said 72 people were killed, and 292 injured in the violence in Cairo.