CAIRO (Reuters) - Thirteen Egyptians were killed in violence between Christians and Muslims as sectarian tensions resurfaced in Cairo and a new government met for the first time on Wednesday, discussing how to restore law and order. The Health Ministry said the 13 people were killed and 140 wounded in violence on Tuesday night ignited by tensions built up since an arson attack on a church south of Cairo . The strife poses another challenge to the ruling Supreme Council of the Armed Forces as it charts Egypt's course towards elections that will return power to a civilian, elected government within six months. The revolution that swept President Hosni Mubarak from power on February 11 was characterised by Christian-Muslim solidarity. Egyptians hoped the uprising had buried tensions that have flared up with increasing regularity in recent years. Meanwhile, dozens of men armed with rocks attacked a few hundred pro-reform protesters in Cairo on Wednesday, seeking to drive them out of Tahrir Square, witnesses said. Later in the day, army officers were seen removing protesters' tents and asking them to leave the square, witnesses said. "The army decided to remove tents and clear the square," a military official said. Small groups of reformists have continued to gather in Tahrir Square since Mubarak was toppled. Numbers have climbed on Fridays when activists have called for bigger participation to press demands for political reform. "A group of gangsters attacked us with stones, they seemed to be wanting us to leave the square," said Gamal Hussein, 60