Supporters of deposed Egyptian President Mohammad Mursi manned makeshift barriers as they braced for a crackdown as early as Monday on their Cairo protest camps following the expiry of a government ultimatum.

Supporters of deposed Egyptian President Mohammad Mursi manned makeshift barriers as they braced for a crackdown as early as Monday on their Cairo protest camps following the expiry of a government ultimatum.

Mursi loyalists, led by his Muslim Brotherhood movement, have kept in place two huge protest camps in the capital and have also staged almost daily demonstrations around Egypt against the Islamist leader's July 3 ouster.

The country's interim leaders have repeatedly warned them to leave, even promising the Brotherhood a return to political life for an end to the protests.

With over 250 people killed since Mursi was overthrown and detained, authorities say they are eager to avoid more bloodshed.

The dispersal of the sit-ins will be "gradual", with protesters given "several warnings" before police move in, senior security officials told AFP.

"There will be a series of gradual steps. We will announce every step along the way," an interior ministry general told AFP.

Once the siege begins, the protesters will be "surrounded", no one will be let into the sit-ins and the protesters will be given several warnings to leave, another security official said.

"This will last two to three days," he said.

In parallel, at the main Rabaa Al-Adawiya sit-in, dozens of men wearing helmets and holding clubs on Monday guarded makeshift brickwall barriers.