Sudan has lodged a complaint against Chad with the UN Security Council, after accusing its neighbour of bombing targets in Darfur last week, state media reported on Monday.
Sudan said two Chadian aircraft bombed the Umm Dukhun area of West Darfur state on Thursday, an area believed to be the base for Chadian rebels opposed to the rule of President Idriss Deby Itno.
"Sudan has delivered to the UN Security Council a complaint against the Chadian violations and the repeated aggressions," Sudan's ambassador to the UN Abdul-Mahmoud Abdul-Halim was quoted as saying by the state SUNA news agency.
Abdul-Halim said Sudan retained the "full right to repulse such irresponsible acts," calling the alleged raids "criminal and unjustifiable".
Reports of fresh conflict in the border region raised fears of wider hostilities between the two neighbours, although Sudan has said it will stick to previous agreements unless threatened further.
Sudan also accused "some forces in the Security Council" of supporting the reported attacks.
He did not elaborate but Chad's former colonial ruler France, which is a veto-wielding permanent member of the Security Council, has supported its ripostes to rebel attacks in the past.
Ndjamena has denied Khartoum's accusations, saying it only bombed rebel positions within its own territory.
Chadian rebels from the Union of Forces of Resistance said several civilians were killed during raids inside Chad on Thursday. The claim could not be independently verified.