Egyptian officials now believe that an attack on a church which killed at least 21 worshippers in Alexandria was the work of a suicide bomber. Earlier the blast outside the church was said to have been caused by a car bomb. At least 43 people were wounded by the explosion, officials said. The blast hit worshippers as they left a new year's service at the al-Qidiseen church shortly after midnight. Christians and Muslims clashed briefly after the attack. "It is likely that the device which exploded was carried by a suicide bomber who died among others," Egypt's interior ministry said in a statement. After the explosion, angry Coptic Christians clashed with police and local Muslims, reportedly throwing stones and targeting a nearby mosque. Protesters went into the mosque, throwing books out onto the street, the Associated Press news agency reported. The mosque had also been damaged by the bomb. A large contingent of police rushed to the scene and used tear gas to disperse the crowd. The situation is reported to be under control now, but BBC reporter Assad Sawey says it is still very tense. It is not known who carried out the attack. The casualties included eight injured Muslims, the health ministry said. Our correspondent says relatives are being denied access to the victims' bodies at the morgue and it is not clear when they will be buried. Christians in the Coptic Orthodox Church make up about 10% of Egypt's population, most of whom are Muslims. Sectarian tensions In recent months Copts have complained of discrimination, while some Muslims accuse churches of holding converts to Islam against their will, our correspondent reports. The mayor of Alexandria, Gen Adel Labib, said on Egyptian TV that there had been recent threats of attacks on churches. A local priest said the death toll from the blast would have been even higher had the explosion happened minutes later, after more people had left the service, reports the BBC's Khaled Ezzelarab in Cairo. After the explosion, Christians were seen chanting beside a burnt-out car in front of the church: "We sacrifice our souls and blood for the Cross." Al-Qaeda in Iraq has also been conducting a campaign against Christians, following the reported conversion to Islam by two Egyptian Christian women in order to divorce their husbands. The group said the women were being held against their will by the Coptic Church. Alexandria, Egypt's second-largest city with a population of about four million, has seen sectarian violence in the past. In 2006, there were days of clashes between Copts and Muslims after a Copt was stabbed to death during a knife attack on three of the city's churches. Source: BBC