CAIRO — Supporters of toppled President Mohammed Morsi increased the pressure on Egypt’s interim leadership by defiantly flooding into two protest camps Monday, prompting police to postpone moving against the 6-week-old sit-ins because they feared a “massacre.”

Morsi’s Islamist backers have rejected negotiations with the military-backed government, leaving the most populous Arab nation in an uneasy limbo.

Still, the delay by the security forces gave the Sunni Muslim world’s top religious institution more time to try to ease tensions with a new initiative.

Authorities also showed no signs of meeting key demands by Morsi’s Muslim Brotherhood to release top Islamists who have been detained and face criminal investigations.

A judge ordered the deposed president, detained sinceJuly 3, to be held for 15 more days pending investigations of charges he conspired in 2011 with Palestinian militants.