A bomb explosion on Monday in a tunnel near Aleppo Citadel in Syria damaged a wall of the fortress that is part of the UNESCO-listed Old City, state media and a monitor reported. The blast partly destroyed the wall of the monumental 13th century citadel that overlooks the Old City, said the official SANA news agency and the Syrian Observatory for Human Rights. “A powerful explosion was heard after midnight Saturday. It was caused by the blowing up of a tunnel in the Old City near the Aleppo Citadel,” the Observatory said. “The blast caused the collapse of part of the wall of the citadel,” said Observatory chief Rami Abdel Rahman. The Observatory said the rebels dug the tunnel “but it was the regime which blew it up to prevent them from reaching an army position”. The explosion was followed by clashes between rebels and government forces battling for control of the city.