A total of 55 people have been detained in three days of clashes between Coptic Christians and Muslims in Egypt's second largest city Alexandria, a state newspaper reported on Monday.

"Prosecutors in Alexandria quizzed 55 suspects held over rioting, which erupted in the city and injured 31 people, including three policemen," said the Egyptian Gazette, an English daily.

Around 38 stores and 32 cars were damaged in the violence, police sources were quoted as saying.

A mentally-ill man attacked two Coptic churches in Alexandria on Friday, killing one elderly worshipper and injuring five others, including one who died later of wounds sustained in the attack.

Angry Christians have clashed in various areas in the city during the last three days as Egyptian security forces tightened protection for churches and mosques in the country.

Source: Xinhua