Tension is mounting in the Egyptian capital Cairo after the military staged an apparent show of strength during a sixth day of anti-government protests.Two air force jets and a helicopter repeatedly flew low over Tahrir (Liberation) Square, the main gathering point for demonstrators.
A column of tanks arrived there only to have its path blocked by protesters.
Meanwhile, US Secretary of State Hillary Clinton has called for an "orderly transition" of power in Egypt.
"We want to see restraint, we do not want to see violence by any security forces," she told ABC News.
The BBC's Jeremy Bowen, in Tahrir Square, says there is a mood of defiance among the anti-government protesters there, who are accusing the military of trying to intimidate them.
Earlier, despite the presence of armoured vehicles, the protesters appeared to have free rein in the city centre, with no sign of the riot police with whom they have clashed violently in recent days.
At one point, an army officer was carried aloft on the shoulders of cheering protesters.