Military forces at the presidential palace on December 6, 2012 - Aswat Masriya
CAIRO, Jan 12 (Reuters) - Unknown attackers threw petrol bombs at tents housing protesters outside the Egyptian presidential palace in Cairo on Saturday, witnesses said.
A Reuters reporter saw several tents on fire and ambulances driving away from the scene late on Saturday evening.
Protesters opposing an Islamist-backed constitution have been camped outside the residence of President Mohamed Mursi for several weeks. (Reporting by Yasmine Saleh and Maria Golovnina; Editing by Rosalind Russell)