Egyptian security sources say at least seven Muslims have been arrested after they destroyed Christian-owned shops and buildings in southern Egypt.

Police on Sunday said the detainees smashed windows, hurled stones and set fire to 13 stores and a church during riots late Saturday in the city of Isna.

Sectarian tensions between Muslims and Christians are commonplace in southern Egypt. But Saturday's riot was reportedly in response to alleged violence against a Muslim girl by Christian boys.

In a separate development Sunday, an Egyptian military court dropped terrorism charges against 40 members of the Muslim Brotherhood.

Legal sources say the defendants still face charges of membership in an illegal organization.

The Brotherhood's number three leader, Khayrat al-Shater is among the defendants.

Egypt's government banned the Brotherhood in 1954.

Authorities often carry out raids against the group. But the Brotherhood operates openly and its members hold more than one fifth of the seats in Egypt's parliament, where they sit as independents.

Some information for this report was provided by AFP, AP and Reuters.