Christians yesterday prayed at a church targeted by an apparent suicide bomber who killed 21 people, as Egypt blamed international terrorism for the attack and fears mounted of sectarian unrest.

“With our soul and our blood, we will redeem the Holy Cross,” the grieving congregation chanted at the Coptic church of Al-Qiddissin in the northern city of Alexandria during Mass, just a day after the bombing.

Bloodstains from the attack were still visible on the façade of the church where 21 people were killed early on New Year’s Day and 79 wounded when an apparent suicide bomber blew himself up.

The attack sparked angry street protests in Alexandria and clashes between hundreds of Christian youths and police.

There has been no early claim of responsibility, but Al-Qaeda has called for punishment of Egypt’s Copts over charges that two priests’ wives they say had converted to Islam were being held by the Coptic Church against their will.

A security official said about 20 people were detained for questioning but there was no evidence any of them was directly connected to the attack.

The Alexandria attack came two months after an Al-Qaeda affiliate claimed responsibility for a deadly Baghdad church raid which it said was aimed at forcing the release of the women in Egypt.

President Hosni Mubarak said the attack bore the hallmark of “foreign hands,” and the interior ministry also blamed “foreign elements” – euphemisms which point to Islamist militants such as Al-Qaeda loyalists.

Mr Mubarak pledged in televised remarks on Saturday that he will “cut off the head of the snake, confront terrorism and defeat it” and urged Egypt’s Christians and Muslims to ­­unite in the face of a common enemy.

At least 5,000 people attended funerals late on Saturday for the victims at a monastery outside Alexandria, where crowds of mourners shouted slogans and refused to accept official condolences.

“No, no, no,” the crowd shouted as a Coptic Church official tried to read out condolences from Mr Mubarak.

Government and independent newspapers warned yesterday that “civil war” could break out in the country unless Muslims and the minority Christians close ranks.

They also urged the government to focus on the situation of the Copts, who account for up to 10 per cent ­of Egypt’s 80 million population and often complain of discrimination.

“Someone wants to make this country explode ... We must realise that there is a plot aimed at triggering religious civil war,” the pro-government daily Rose El-Yussef said.

Christian protesters on ­Saturday heckled police and showered them with stones as they shouted slogans against Mr Mubarak’s regime.

The protests ran on into yesterday. Several dozen demonstrators pelted police with stones in a mainly Coptic neighbourhood of Cairo after they were prevented from demonstrating on a highway, police said.

Police officials also said more than 1,000 Copts demonstrated outside the foreign ministry and neighbouring state television buildings. Some protesters pelted passing traffic, damaging more cars.

In the southern province of Assyut, a protest in the village of Al-Izziya turned violent when Coptic demonstrators assaulted a Muslim and destroyed three cars, a witness said.