Egyptian officials say archaeologists have unearthed the first basilica erected in the Mediterranean port city of Alexandria.

Antiquities authorities say the basilica is dated to the Roman era and was built on the ruins of a temple from the Ptolemaic reign that ended with the death of Cleopatra.

Egyptian Interior Minister Habib al-Adly said on Sunday that a Palestinian group was behind the New Year's church attack in the Mediterranean city of Alexandria that killed more than 20 people.

"The Palestinian Islamic Army, which has links to Al-Qaida, is behind the attack on the al-Qiddissin church in Alexandria," Adly said in a speech to mark Police Day, carried live on state television.

Egypt was on high alert on Monday ahead of the Coptic Christmas holiday following a New Year's Day church bombing that killed 21 people as investigators raced to identify those behind the attack.

Police cancelled leave for top officers and were tightening surveillance of airports and ports to prevent suspects from leaving the country, as new checkpoints were set up across the nation.

Jbeil Maronite Archbishop Beshara Rai said Monday that an Islamic summit should announce its stance from fundamentalists that are attacking Christians in the region.

Islamic and Arab countries should also make a stance from the latest attacks on Christians in Iraq and Egypt, he told LBC TV network.