At least 12 people were killed after a northern Sudanese army convoy entered the contested north-south border region of Abyei, sparking clashes with southern police.

Abyei's top administrator, Deng Arop Kuol, says the fighting broke out Sunday when a Sudanese army convoy entered Abyei despite efforts by southern police to stop them.

Kuol said a dozen people were killed including a policeman.

In comments to Reuters news agency, a northern minister blamed the clashes on police, saying that troops were just joining an internationally recognized north-south force in the area.

Each side regularly accuses the other of sending large numbers of soldiers into the disputed region.

The oil-rich Abyei region was a battleground during Sudan's 21-year north-south civil war.

South Sudan voted overwhelmingly to split from the north in a January referendum that northern leaders have said they will accept.  However, the future of the Abyei region has yet to be resolved.

Last week, Sudanese President Omar al-Bashir warned his government would not recognize south Sudan as an independent state it it did not give up claims on Abyei.

A scheduled referendum on which part of Sudan Abyei would join failed to happen, because the north and south could not agree on who was eligible to vote.