"(The) South Sudan government did not respond to the repeated calls of the international community and continued its hostile activities to undermine the stability and security of Sudan," said the statement carried by the official SUNA news agency.
The statement came after fresh Sudanese air raids against the South drew swift condemnation from the United Nations, United States and France.
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Sudan accuses the South of supporting anti-government rebels from its conflict-hit western region of Darfur as well as those fighting in South Kordofan state and Blue Nile.
The South denies backing opposition movements inside Sudan.
On Friday, US President Barack Obama, while calling on Sudan to cease its aerial bombardments, said South Sudan "must end its support for armed groups inside Sudan and it must cease its military actions across the border."
The foreign ministry said rebels were behind an attack on a joint Sudan-Chad-Central African border force in Darfur.
Eleven Central African troops belonging to the regional task force died in the rebel attack last week on the Sudanese side of the border, officials in Bangui said earlier.
The ministry also referred to repeated rebel attacks on the South Kordofan town of Talodi.
Insurgents from the Sudan People's Liberation Movement-North (SPLM-N) claimed to control part of the strategic town on Sunday night, denying they had suffered heavy losses on the same day South Sudanese forces ended their occupation of the key Heglig oilfield in the southern region.
"The Ministry of Foreign Affairs affirmed that the armed forces maintains the legitimate right... to practise self defence and to pursue the aggressors wherever they are", the statement on SUNA said.
