Undersecretary of the Sudanese Ministry of Foreign Affairs Mutrif Siddiq told reporters that the government had obtained clear-cut evidence on the role of Chad in the Saturday attack of the rebel Justice and Equality Movement (JEM) in Omdurman, northwestern Khartoum.
Siddiq noted that Chad's behavior had led to a cease of effectiveness of an agreement which the two countries signed during a recent Organization of the Islamic Conference (OIC)summit in Dakar, Senegal, in March for normalizing the relations between Sudan and Chad.
Meanwhile, Sudan's envoy to the African Union (AU), Ambassador Mohi-Eddin Salem, lodged a protest to the AU Peace and Security Council against the sabotage attempt in Omdurman and a number of areas in Kordofan region neighboring Darfur which was staged by the JEM rebels through support from the Chadian government.
Early on Sunday, Sudanese President Omer al-Bashir announced a decision to sever diplomatic ties with Chad, holding Chad responsible for the rebel attack on the Sudanese capital.
The Chadian government denied on Sunday accusations made by the Sudanese government that it N'Djamena was involved in the JEM's attack in Khartoum.
"Chad has nothing to do with this adventure," Chadian Information Minister Muhammad Hissein told Qatar-based al-Jazeera television monitored in Khartoum.
He called on the Sudanese government and all the rebel movements in the restive western Sudanese region of Darfur to be committed to the agreements they had signed.
The Sudanese government announced on Saturday evening that the army and the police had crushed the attempt of the JEM rebels to infiltrate into the capital and carry out sabotage activities there, killing and capturing a number of the infiltrators.
It was the first time for rebels in Darfur to enter Khartoum and launch attacks there since bloody conflicts erupted in the western Sudanese region neighboring Chad in February, 2003.
The Sudanese government has repeatedly accused N'djamena of supporting and providing assistance to the rebel movements in Darfur, but the Chadian government has denied the accusation.