Clashes erupted between Sudan and South Sudan's armed forces on Monday, both sides said, prompting Sudan's president to suspend a planned meeting on resolving the countries' bitter disputes over oil and border regions, state media reported.
South Sudan accused Sudan of sending warplanes to bomb two border areas and launching a ground attack on a third.
Sudan accused the southern army of attacking the oil-producing Heglig region, parts of which are claimed by both nations.
The countries have been at loggerheads over a series of sensitive issues since South Sudan declared independence from Sudan in July, taking with it most of the country's known oil reserves.
The neighbours have yet to agree on the position of their 1,800-km (1,120-mile) shared border or how much the landlocked south should pay to export oil - the lifeblood of both economies - through Sudan.
Sudan's President Omar Hassan al- Bashir had been planning to fly to the southern capital Juba on April 3 to meet his southern counterpart Salva Kiir to try and resolve their disputes.
But Bashir decided to suspend the trip after the Heglig attack, Sudan's state radio reported on Monday in a text message alert. It gave no further details and officials in Khartoum could not be reached for comment.
SPLA accuses Sudan of bombing
South Sudan's army, or SPLA, on Monday accused Sudan of bombing the disputed border areas of Jau and Pan Akuach and then moving ground forces against another area called Teshwin.
"After repulsing the attack, the SPLA pursued the withdrawing SAF (Sudanese Armed Forces) force and they captured two bases of SAF between Heglig and Teshwin," SPLA spokesman Philip Aguer said.
"This is a self-defence measure by SPLA to defend itself against aggressors," he said.
Aguer said parts of Heglig were now under control of the southern army, a statement denied by Sudan.
- Lawyer wants Chinedu to appear in court
- Maji marefu’s futile effort to find stolen property
- Diplomatic passports, special number plates for governors
- Can chickens really be cleverer than a toddler? Studies suggest animals can master numeracy and basic engineering
- Freedom of media under threat in Eastern Africa
- Rapid desertification in Kenya threatening livelihood