The army and police are preparing to contain any trouble, adding men and barriers around important public buildings.

Mursi has given no hint of the contents of what aides called an “important speech”, to start around 9:30 p.m. (3:30 p.m. EDT) at a Cairo stadium before an invited crowd. Some speculate he may reshuffle his cabinet to try to defuse the anger against him.

Some observers fear Egypt may be about to erupt again, through a combination of political polarization since the revolution that overthrew Hosni Mubarak and an economic slump that means Mursi’s government is fast running out of cash.

While a number of his critics worry about Islamist rule, most appear simply frustrated by falling living standards.