|South Sudanese will vote on January 9 on whether the region should become independent [AFP]
South Sudan's president has asked UN Security Council envoys to deploy peacekeepers along the
Sudan's north-south border in the run-up to a referendum on southern independence, diplomats say.
Saturday's news of the request from Salva Kiir came amid growing tensions along the ill-defined border. Both sides have accused each other of building up troops there.
A diplomat said the request would be considered but the envoys made no promises.
The northern government said on Thursday that the main party of the south, Sudan People's Liberation Movement (SPLM), is deploying forces in border areas.
"The massing of military forces by the SPLM in borders’ areas is a clear violation to the protocols of security arrangement," Sawarmi Khaled, a Sudanese military spokesman, said.
"It is considered an antagonistic act because the protocols commit the SPLM to limit its forces only to places agreed on in the peace treaty."
But the SPLM on Friday said it is the Sudanese military from the north that is gearing up for fighting.
"The Sudanese army is looking for a way to initiate a war," Kuol Diem Kuol, an SPLM army spokesman, said.
"I challenge the Sudanese army to allow the UN forces in southern Sudan to investigate who is gearing up forces. Is it us or the Sudanese army?"
Under a 2005 peace agreement that ended Africa's longest-running civil war, the south is to vote on January 9 on whether to become independent or to remain part of a united Sudan.
Simultaneously, the disputed border region of Abyei will vote on whether the region should belong to the north or the south.
Mohamed Adow, reporting from Khartoum, said it is not the first time the two sides are accusing each other of massing troops at the border, near Abyei.
"It's coming at a time when there has been tension and a stalemate over the composition of the referendum commission for Abyei," he said.
"Parties are negotiating right now in Addis Ababa but so far there has been nothing tangible coming out of the talks. The parties are discussing the composition of the referendum commission and who will be eligible to vote."
Abyei's referendum law gives the right of vote to members of the southern Dinka Ngok tribe and it is up to the referendum commission to decide which "other Sudanese" are considered residents of the region and therefore eligible to vote.
The ruling National Congress Party says the Misseriya, a big pro-unity nomadic tribe which grazes its cattle in the south during the dry season, should also vote.
The SPLM says the tribe as a bloc should not be allowed to vote, but that individuals with long-term residence in the region should be able to do so.
South Sudan independence supporters tussled with riot police and pro-unity campaigners in Khartoum on Saturday, in a rare public display of the growing divisions around a looming southern secession referendum.
In the capital, Khartoum, a group of up to 40 southerners, waving banners and shouting slogans calling for independence, turned up at a 2,000-strong rally in support of Sudan's president. The protest was timed to coincide with the visit of UN Security Council envoys to the capital.
Riot police moved in after pro-unity supporters approached the southerners and shouted at them to leave and pushed towards the group.
The bitter war between north and south Sudan, lasting for more than two decades, left an estimated two million people dead.
A peace deal signed in 2005 created a federal unity government that shared power between the north's ruling party and the former southern rebels.