Protesters blocked the entrance to Egypt's cabinet headquarters on Friday in a bid to prevent newly-named Prime Minister Kamal al-Ganzuri from entering the building, an AFP reporter said.
The action was in protest at Ganzuri's appointment, one of the organisers, Ahmed Zahran, told AFP, adding that a news conference would follow shortly.
Hundreds standing outside the building just blocks from Tahrir Square, the epicentre of demonstrations, chanted "Leave! Revolution! Ganzuri is a former regime leftover."
Ganzuri himself said earlier on Friday that a new cabinet will not be finalised before parliamentary elections which start next week, and that he did not yet plan to go to the building.
Egypt's ruling military council named Ganzuri, who served as premier under ousted president Hosni Mubarak, to the dismay of protesters who want a new figure to lead the transition to democratic rule.
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Outside the headquarters, protesters said they were eager to prevent any damage to the building.
"We are protecting the building. We are organised so that we can protect our reputation," said protester Omar Abdel Mansur, 35.
Pro-democracy groups had put forward several names including UN nuclear watchdog chief Mohamed ElBaradei and ex-Arab League secretary general Amr Mussa to lead a national salvation government.
"The youth of Tahrir had proposed (several) names. None of them were chosen. We have the feeling nothing has changed," since a popular uprising ousted Mubarak in February, said Mohammed Khattab, 30.
"Our mistake in the (January-February) revolution was to think that we had only to topple Mubarak."
Protesters camped out in Tahrir Square for the past week have been demanding that the ruling Supreme Council of the Armed Forces hand over power to a civilian authority.
At least 41 people have died in clashes between police and the protesters since last Sunday, and more than 3,000 people have been injured.