Sudan has accused Chad of carrying out air raids inside its territory, and said it is assessing how to respond, BBC reported.

One Sudanese official described the alleged raids as an act of war and said there had been casualties - though another official said no-one was hurt.

The accusation comes 10 days after Chad said Sudan had carried out an attack.

The two states have long traded accusations of supporting rebels in each other's territory, especially around Sudan's war-torn Darfur area.

On Friday, Sudanese foreign ministry spokesman Ali Sadiq said two Chadian aeroplanes had carried out strikes on areas 60km (40 miles) inside Sudan.

The raids had taken place in deserted areas and there were no casualties, he was quoted as saying by AFP news agency.

But Ali Youssef Ahmed, head of protocol at Sudan's foreign ministry, was quoted by Reuters news agency as saying: "They attacked. They bombed and there were casualties."

Sudan has summoned the Chadian ambassador and alerted the UN Security Council, the Arab League and the African Union, Mr Sadiq said.

"The Sudanese army is ready to respond but is waiting for instructions from the leadership," he said.