Egyptian medical sources say at least 19 people were killed and 150 injured Sunday when Coptic Christians protesting a recent attack on a church clashed with security forces in the capital, Cairo.

Rioters used firebombs, set army vehicles on fire and battled with security forces outside the state television building, in Egypt's latest sectarian flare-up. Hundreds of protesters fought with police, some of them tearing up pavement and using rocks for ammunition.

Christian protesters said their demonstration began peacefully but that plainclothes police attacked them. The protests later spread to Tahrir Square, the focal point of the February uprising that ousted former president Hosni Mubarak.

In the past few weeks, riots have broken out at two churches in southern Egypt, prompted by Muslim crowds angry about church construction.

One clash took place near the city of Aswan, after church officials agreed to a demand by local ultra-conservative Muslims – known as Salafis – that a cross and bells be removed from the church building.

Aswan's governor, Mustafa Kamel al-Sayyed, is also reported to have suggested that the church does not have legal authorization. Protesters said Sunday they are demanding the governor's ouster after the church was partially demolished last week.

Christians make up about a tenth of Egypt's 80 million people and often face attacks from Islamic extremists. Copts joined with Muslims during the protests that ousted Mr. Mubarak, but sectarian troubles have since intensified.

Egypt has been considering new laws designed to stem sectarian violence, including banning protests at places of worship and the use of religious slogans to incite hatred.

In May, 12 people were killed in sectarian clashes between Christians and Muslims after rumors spread that Christians were holding a woman who had converted to Islam.