The UN and the African Union have applauded the ceasefire agreed by Sudan
and two rebel groups from Darfur.
Refugees say militias raid villages after attacks by helicopter gunships
UN Secretary-General Kofi Annan called for an immediate end to attacks on civilians and access for aid workers.
Some 670,000 people have fled Darfur but remain inside Sudan, with little humanitarian help.
The three groups reached a deal at talks in neighbouring Chad, which now hosts 100,000 refugees who fled alleged "ethnic cleansing" by Arab militias.
An AU statement urged all sides to reconvene very soon to expand the truce into a comprehensive peace agreement.
The ceasefire - signed by the government and the rebel Sudanese Liberation Army (SLA) and Justice and Equality Movement (JEM) - will begin within 72 hours and will stay in place for 45 days.
The agreement called for final peace talks to begin within 15 days.
The three sides agreed to allow aid agencies access to Darfur and to free prisoners of war.
"There is no winner, there is no loser. We reached a consensus and the only winner is Darfur and Sudan," said Sudanese Investment Minister Sharif Ahmed Omar Badr - the government's representative at the talks, quoted by the AP news agency.
"We managed, through painful negotiations, to reach an
agreement," said the SLA's negotiator, Dr Sharif Harir.
On Wednesday, in a speech to mark Rwanda's genocide, UN Secretary General Kofi Annan warned that if Sudan denied aid workers access "the international community must be prepared to take swift and appropriate action... which may include military action".
He said the world could not stand by as it had during Rwanda's genocide 10 years ago.
US President George W Bush also pressed the Sudan government, saying it "must not remain complicit in the brutalisation of Darfur".
Sudan analyst Eva Dadrian from the Africa Analysis newsletter said it will be hard for the government to reign in the Arab militia - the Janjaweed - which have been leading the attacks on black African civilians in Darfur.
"Darfur is a very vast region and the government will have difficulty to control these people. The Janjaweed are everywhere. They hide in the mountains," she told the BBC Network Africa programme.
The fighting in Darfur has been raging for more than a year, with rebels claiming that the Arab-dominated government is ignoring the region.
Last week, UN emergency relief co-ordinator Jan Egeland accused the government in Khartoum of tolerating "ethnic cleansing" by Arab militias.
The refugees say that attacks on their villages by helicopter gunships are followed up the Janjaweed on horses and camels, who rape, kill and loot.
The Sudanese government has denied the allegations.
'Southern deal soon'
There is also hope of a final peace deal with rebels in southern Sudan.
The rebellion there has raged for 20 years and also pits blacks against the Arab government.
There is also hope of a peace deal in the south
The two sides have reached a "90%" agreement, US officials say.
"We're expecting to finish the remaining issues and to sign an agreement on the power-sharing and the three areas latest by Saturday," rebel spokesman Yasir Arman said.
They have not yet agreed on how to share power during a six-year transition period or on the status of three states claimed by both sides.