At least 21 people have been killed after a bomb exploded inside a packed Egyptian church as worshippers marked Palm Sunday. Thirty-eight are also injured, said Magdi Awad, head of the provincial ambulance service. State television, meanwhile, put the number at 42. The explosion happened in the city of Tanta - about 55 miles north of Cairo. Video and pictures, reportedly showing the aftermath, show crowds gathered around bodies and large blood stains on the pews and church walls. Egypt is home to around nine million Coptic Christians and there have been previous attacks on them by groups linked to Islamic State.