CAIRO, July 16 (Reuters) - Egyptian authorities have arrested 401 people over clashes that took place in Cairo overnight when supporters of Mohamed Mursi battled security forces and the ousted president's opponents, the state news agency MENA said on Tuesday.

"A security source confirmed that security forces have succeeded in arresting 401 people provoking unrest during the clashes," MENA said. (Writing by Alexander Dziadosz; Editing by Alison Williams)