Clashes between supporters and opponents of President Mohammed Morsi have erupted in Egypt, killing at least one and injuring hundreds more.
About 230 people were hurt in the violence on Wednesday as the Egyptian president prepared to address the nation amid growing calls for him to step down.
Fears of a showdown in the streets between Morsi's Islamist supporters and a broad coalition of the opposition parties on have led people to stock up on food and buy up fuel supplies.
In Cairo's Tahrir Square hundreds of anti-Morsi protesters have gathered to watch the president's speech.
The army and police are preparing to contain any trouble, adding men and barriers around important public buildings.
Also on Wednesday, Egypt's military brought in reinforcements of troops and armor to bases near Egyptian cities ahead of expected June 30 protests.
Morsi has given no hint of the contents of what aides called an "important speech", to start around 9:30 pm local time, 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 polarisation since the
revolution that overthrew Hosni Mubarak, and an economic slump that hurts ordinary Egyptians.
While a number of his critics worry about Islamist rule, most appear simply frustrated by falling living standards.
Washington has urged him to bring the opposition into the political process and to press ahead with economic reforms.
All sides insist they do not want violence, but there have been scuffles and deaths in recent days.
The army has warned it could step back in, a year after it handed power to the elected president.
Residents saw tanks taking up positions near a major highway running into Cairo.
The army is held in high regard by Egyptians, especially since it pushed aside Mubarak following the 2011 uprising.
Nationwide opposition rallies are due to start on Sunday, but could begin earlier.
In his speech, Morsi may offer a rundown of achievements since he became Egypt's first freely chosen leader and explain how he plans to end a mounting budget crisis.
He has had help from Qatar and other oil-rich Arab states but major reforms, including cuts to fuel and food subsidies, may be needed.
He may also replace Prime Minister Hisham Kandil with a figure from among the secular opposition.
There is also talk on social media of some more spectacular move, including turning to the army or calling elections.
The opposition, however, has low expectations.
Liberal activists plan to watch the speech on an open-air screen in Cairo's Tahrir Square, where the revolt against Mubarak began in January 2011.