Although the Darfur rebels have little chance of toppling Sudan's regime, the advance is "the first time anyone has managed to take civil war to the doorstep of the [Sudanese] government, so it's a propaganda victory of sorts," says Richard Cornwell of the Institute for Security Studies in South Africa.
The move by the Justice and Equality (JEM) rebel group may expose the fragility of the Sudanese government by putting pressure on existing divisions, say analysts. But it also gives Khartoum a reason to ramp up its latest offensives in Darfur and raises the prospect of a border war between Chad and Sudan; both believe the other is using rebels as proxy fighters.
"The government has already begun to manipulate this," says Salih Mahmoud Osman, a Darfuri member of parliament, explaining that Khartoum now has the political cover it needs to step up its offensives in Darfur and to stall elections. "They are already blaming Chad, a number of people have been arrested, and they can say the country is under external threat."
A surprise assault on Khartoum
This weekend's rebel assault came out of the blue.
Several hundred JEM rebels launched their attack on Saturday morning having traveled more than 600 miles from their Darfur strongholds.
Sudanese armed forces responded with artillery and helicopter gunships as fighting raged through the day.
Sunday morning, President Omar al-Bashir appeared on state television, dressed in military uniform, to say the attack had been repelled and that he would sever ties with Chad.
"These forces are all basically Chadian forces supported and prepared by Chad and they moved from Chad under the leadership of Khalil Ibrahim," he said in a televised address, adding that he reserved the right to retaliate against the "outlaw regime."
Mr. Ibrahim, who leads JEM, is from the same Zaghawa tribe as Idriss Deby, president of Chad.
Although he denies being backed by Chad, the ties are an open secret.
In February, JEM fighters traveled from Darfur to Chad to protect Mr. Deby from rebels pouring into his capital, N'Djamena.
At the same time, links between Khartoum and Chadian rebels are barely disguised.
Their use of the French language and distinctive, open-topped pickups make them easy to spot.
Proxy war payback
"It seems that, at least in part, this is payback for [Sudan's ruling National Congress Party's] support for rebels in Chad who almost toppled the government there in February," he said.
With the rainy season just beginning in Darfur, it was also one of the last chances for JEM to strengthen its hand before hunkering down for the next few months.
Security sources in Khartoum, speaking on condition of anonymity, estimated that about 200 rebel technicals – pickups mounted with heavy machine guns – made the three-day journey from their strongholds in the Jebel Moon region of West Darfur.
They crossed into North Darfur and then Northern Kordofan using areas controlled by sympathetic tribes.
They picked up reinforcements along the way, before approaching Khartoum from the west via its historic neighbor Omdurman.
The city is well-defended with machine gun emplacements along all major arteries and around strategic position such as airports and government buildings.
Bridges across the Nile were closed as fighting began.
Suleiman Sandal, JEM's deputy chief of staff, told the Agence France-Presse news agency that his forces had struggled to adapt to urban warfare.
"Our troops came from Darfur," said Sandal, who claimed he was still in Omdurman on Sunday. "This is the first time for them to fight in towns and now we are gathering our troops and thinking about what we're doing."
Latest United Nations estimates put the death toll in Darfur at 300,000 since rebels took up arms against what they see as an Arab-dominated government in Khartoum.
Yet after five years the fighting has had little impact on the capital, where an oil-fueled building boom has seen new hotels and office blocks springing up beside the Nile.
A foreign aid worker, who is not authorized to speak to the media, says the latest attack had changed all that.
"People here are very frightened. It always seemed as if the war was hundreds of miles away – which it was," he says.
By creating fear in the capital, the rebels might also hope to point up the fact that the government is divided and that the city contains opposition elements made up of southerners and Darfuris, says Mr. Cornwell. But the result is likely to be "a crackdown by the authorities" on the opposition.