There has been a flare-up of fighting in north-eastern Sudan, with rebel groups saying that they started a major offensive.
As in Darfur, the government is accused of ignoring the east
These clashes come on top of a two-year conflict in the western region of Darfur, which has left at least 180,000 dead, and a deal to end 22 years of conflict in the south.
What is the fighting in the east about?
As in Darfur and the south, residents of eastern Sudan say they have been ignored by the central government in Khartoum.
They say the east is poorer than other areas, with fewer state services, such as schools, hospitals and roads.
The Beja and Rashaida communities say they have been discriminated against, with Arabs being favoured.
The government has also cracked down on a local form of Islam, further alienating some people.
Are there any links between the three rebellions?
One Darfur rebel group, the Justice and Equality Movement (Jem) has backed the Eastern Front.
Although Darfur is some 1,000km away, Jem's headquarters are in Eritrea, which Sudan accuses of backing the eastern rebels.
Eritrea denies this but says it gives the rebels political support.
Jem has links to Islamist opposition leader Hassan al-Turabi and has always presented itself as a national movement, rather than a Darfur rebel group, experts say.
The leader of the southern rebels, John Garang, who is due to become vice-president under January's peace deal, says he sympathises with the other two rebellions.
Some analysts say that agreement, under which Khartoum agreed to share power and wealth, has encouraged other groups to take up arms hoping to cut similar deals.
The discovery of oil, which is exported through Port Sudan in the east, also means there is now more wealth to fight over.
How strong are the eastern rebels?
This is not clear.
Sudan analyst Julie Flint says that so far, they have adopted the guerrilla "hit and run" tactics used in Darfur.
There are fears that a strong government crackdown could lead to similar scenes of misery seen in Darfur and, previously, in the south.
In both cases, the government is believed to have armed local Arab groups, who pursued a scorched earth policy against communities seen as pro-rebel.
Have there been any attempts to resolve the problems in the east?
Julie Flint says that the government set up a body to discuss the demands of the eastern groups but this used local pro-government groups, instead of rebels leaders.
She says some of these delegates have been attacked.
As part of the agreement to end the war in the south, a new national constitution is supposed to be introduced.
Optimists say that this might redefine the relationship between Khartoum and the regions, ensuring a fairer spread of resources and so ending the rebellions.
But for now, this looks like a distant prospect.