Sudan Sunday severed diplomatic ties with Chad, accusing its neighbor of backing a first ever Darfur rebel assault on Khartoum, and partly lifted a curfew amid its clampdown on remaining rebels. The government said it had repulsed the assault by the Justice and Equality Movement (JEM), allegedly backed by Ndjamena, which saw the insurgents reach Khartoum's outskirts with the declared intent of toppling the regime. “We are forced to sever diplomatic relations with this regime” in Chad, President Omar Al-Beshir said on state television following the attack on the capital's twin city of Omdurman just across the river Nile. “We place the entire responsibility for this attack on Chad,” he said. The Chadian government said it regretted Khartoum's decision to break off diplomatic relations. “Chad can only take note of this hasty decision with regret,” said a statement. The Chadian government had learnt of Sudan's decision “with the greatest surprise,” said the statement. The statement also deplored the fact that its embassy in Khartoum had been ransacked. Police spokesman Major General Mohamed Abduil Majeed said a curfew had been lifted in Khartoum but remained in force in Omdurman until further notice. An Arab League statement said the attack on the capital was a “terrorist operation”. The statement “called on all states that support armed rebel movements to stop backing them or allowing them to use their territories to threaten the unity, security and stability of Sudan,” in an apparent reference to Chad. The Egyptian news agency MENA said Khartoum international airport was closed for security reasons. Remnant rebel forces were still in a number of residential areas in Omdurman, and the corpses of rebels, arms and explosives were being collected, the police spokesman told Sudan's official SUNA news agency. Sudan, meanwhile, said it had opened a telephone hotline and offered a $123 million reward for JEM leader Khalil Ibrahim, SUNA reported. The rebels “are now either dead or prisoners of war,” army spokesman Brigadier General Osman Al-Aghbash told public radio. The army said that “most of those who fell into our hands were Chadian,” and that they numbered around 100. “There are certainly dead and wounded, but we can't say how many,” a spokesman said. JEM's deputy chief of staff Suleiman Sandal said that his forces had taken Omdurman but were having trouble with the urban fighting environment having come from the desert of Darfur, and had suffered deaths and injuries. Sudan and Chad accuse each other of backing rebels seeking to topple their respective regimes