South Africa's public broadcaster has said it refused to broadcast a campaign message from the Economic Freedom Front
The leaders of Sudan and South Sudan have reaffirmed their commitment to setting up a buffer zone on their shared border and resuming oil exports.
African Union mediator Thabo Mbeki said both sides had agreed "unconditionally" to implement a deal first struck in September.
Presidents Omar al-Bashir of Sudan and Salva Kiir of South Sudan smiled and shook hands, but made no comment.
The neighbours came close to war after the South's independence in 2011.
The talks in the Ethiopian capital, Addis Ababa, followed reports of renewed clashes on the disputed border.
African Union mediators will now lay out a timetable for the implementation of all outstanding agreements, according to an official document seen by the BBC.
This is expected to be in place by the end of next week, and if the timetable is respected, a demilitarised buffer zone between the two countries will be set up.
That would allow the resumption of oil exports from the south and of cross-border trade.
"They've... agreed that actions should be taken immediately - or maybe as soon as possible - to implement all the existing agreements unconditionally," Mr Mbeki said.
"The presidents have also agreed that... the necessary decisions are taken to create the safe demilitarised border zone."
BBC Sudan reporter James Copnall says there appears to have been some limited progress on the disputed Abyei region, including a commitment to set up a joint administration for the area, as well as on several other outstanding issues.
But he adds that in essence both leaders have simply agreed to implement deals they had already signed - and the fact that this is necessary gives an indication of just how bad the relationship is between the two Sudans.
The South shut down its own production a year ago as part of a row with Khartoum about how much it should pay to export its oil through Sudan.
The flashpoint region of Abyei is claimed by both sides. It lies on their border and is inhabited both by nomadic herdsmen who are loyal to Sudan and other groups who are closely linked to the South.
Tensions over oil and security brought the two sides to the brink of war last April.
At a meeting in September the buffer zone was agreed and South Sudan said it would resume the production of oil, but the deal was not implemented.
Both sides blamed the other for the lack of progress.
South Sudan, where people chiefly follow the Christian faith or traditional indigenous religions, gained independence in 2011 after more than two decades of civil war with the mainly Muslim north.
Both sides also accuse the other of supporting rebel groups on its territory.