Cairo tense after night of clashes

The Egyptian government has warned that it will crack down on those who threaten the country's security with "an iron fist".

Tension remains in Cairo after clashes between Muslims and Christians on Saturday night, in which two churches were set on fire, 12 people died and 180 were wounded.

The fighting started when Muslims accused Christians of detaining a woman who had converted to Islam.

Jonathan Head reports from Cairo.