The claim came after clashes between government forces and fighters from JEM in Omdurman, on the western bank of the Nile opposite Khartoum.
 

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Abdel Haleem al-Mutafi, Khartoum's governor, told the Reuters news agency that the army was still operating in the outskirts of Omdurman, west of Khartoum, so the curfew would remain in place there.

Jan Eliasson, the UN envoy on Darfur, told Al Jazeera that the JEM has nothing to gain from the attack.

"I told representatives of JEM they will not achieve any sense of victory from this situation," he said.

"I fear the situation may get out of control, and this will prove disastrous to the people of Darfur."

 
Chad ties cut
 
Sudan broke off diplomatic relations with Chad on Sunday, accusing its neighbour of involvement in the previous day's attack.

"We are now cutting our diplomatic relations with this regime," Omar Hassan al-Bashir, the Sudanese president, said on state television.

"These forces [behind the attack] are all basically Chadian forces supported and prepared by Chad and they moved from Chad under the leadership of Khalil Ibrahim."
   
But the Chadian government denied "all involvement" .
 
"The government denies all involvement in this adventure which  it condemns unreservedly, regardless of who was responsible," Mahamat Hissene, a government spokesman, said in a statement.

 

"The Chadian government, which has always supported efforts for  peace in Sudan and in the region, encourages authorities and the  opposition [Sudanese rebels] to maintain the voice of dialogue."

 
Widening conflict
 
The Omdurman incursion was the first time that the conflict raging in western Sudan had reached the capital.
 
The violence in western Sudan has killed thousands and left miliions displaced.
 
Fighters from JEM described Saturday's incursion as a "success".
 
But Ibrahim Mahmoud, Sudan's interior minister, said the fighters had been "chased away" three hours after the attack began.
 
Government soldiers later paraded what they called seized weapons and captured fighters.
 
JEM's claims
 
JEM's website said that its fighters had taken control of Wadi Saidna air force base, just north of Khartoum, during the raid.
 
Eltahir Elkaki, general-secretary of JEM's legislative council, told Al Jazeera by telephone from Libya that "the war will be no longer only in Darfur".
 
"We haven't changed our tactics," he said. "From the beginning, JEM is a national movement and it has a national agenda.
 
"We are now in Khartoum and, hopefully, we will be everywhere in the country."
 
Al-Musalami al-Kabashi, Al Jazeera's Khartoum bureau chief, confirmed that the clashes were limited to Omdurman and did not reach Khartoum.