Embattled Liberian President Charles Taylor has vowed to "fight to the last man", as rebels continued their advance on the capital Monrovia.
Taylor accused rebels of acting in bad faith
Mr Taylor also reiterated his pledge to step down and accept asylum in Nigeria, but only after multinational peacekeeping force arrives in sufficient numbers.
"I will stand and fight to the last man until they (rebels) stop killing my own people," Mr Taylor told Associated Press news agency.
Earlier on Saturday, the government said that rebel forces entered Monrovia after taking a crucial river crossing.
Army commander General Benjamin Yeaten said the rebels had pushed his forces back from St Paul's Bridge and were making their way towards the port.
Defence Minister Daniel Chea said 20 civilians were killed in what he called a flagrant violation of the current ceasefire.
Mr Chea also called on the West African regional organisation, Ecowas, to intervene to stop the violence.
If confirmed, this will be the third time in less than two months that the rebels have entered the city.
On previous occasions hundreds of civilians were killed and thousands made homeless.
"The sounds are terrifying. We want to move, but besides not knowing where it's safe to go to, we don't want our homes looted if we leave," one woman said.
But in an extraordinary show of defiance earlier, as the rebels advanced towards the bridge, thousands of the city's residents took to the streets to protest against the fighting.
Marching towards the front line at St Paul's Bridge, waving tree branches, which are a local symbol of peace, they chanted "We want peace, no more war."
They were determined to march all the way to the rebels, from the main group, Liberians United for Reconciliation and Democracy (Lurd), but were turned back by the government troops defending the bridge.
The rebel leaders at peace talks along the west African coast in Ghana say their men are acting defensively, trying to retake the territory they held when the ceasefire was agreed a month ago.
West African peace monitors are due in Liberia shortly to begin drawing up the map which shows ceasefire positions.
And our correspondent says this battle appears to be last minute jockeying for position.
It had been hoped that a peacekeeping force from the Unites States could avert a bloodbath, but the US has said it will consider sending troops to Liberia only if President Charles Taylor steps down.
A UN envoy has said the US will not take a decision on whether to send troops into Liberia until a local, West African force is in place.
The envoy, Jacques Klein, said the key thing was that troops from Ecowas - the Economic Community of West African States - should go into Liberia quickly, to end the clashes.
It is the third time this month that rebels have sent the population fleeing
Liberian Information Minister Reginald Goodrich said he wanted to see the deployment of peacekeepers promised.
"Everyone is talking about sending troops, but no one wants to send them. What is the delay?" Mr Goodrich said.
He said the fighting proved Lurd rebels were not "serious" about peace.
"[President Charles] Taylor is not the problem."
Mr Klein said Mr Taylor, would be expected to go into exile - most likely Nigeria - on the day the first American troops arrived.