CAIRO — Police have fired tear gas as clashes erupted during rallies by hundreds of supporters of Egypt's Islamist president in front of government buildings in the heart of Cairo.

Security officials and witnesses say the fighting broke out Tuesday when the Muslim Brotherhood, which is demanding that President Mohammed Morsi be reinstated, tried to break into the Interior Ministry where they said members are being held.

Protesters threw rocks at police trying to stop them, prompting the tear gas as local residents joined security forces and began throwing rocks at the Brotherhood supporters.

The violence came a day after Egypt's military-backed leadership postponed a plan to besiege two protest camps occupied by Morsi's supporters to avoid bloodshed.