Juba, Sudan (Agencies): 20 people were killed in a rebellion by former pro-Khartoum militiamen in south Sudan against giving up their heavy weapons which sparked two days of clashes in one of the region's three main towns, a military spokesman said on Saturday.

At least 24 people were wounded in the fighting in Malakal, capital of sensitive Upper Nile state close to the border with the north, said Philip Aguer, spokesman for the former rebel Sudan People's Liberation Army (SPLA).

"There was heavy fighting with mortars fired by both sides, but the clashes have now been brought under control," Aguer said.

"Our forces in the SPLA, along with the United Nations peacekeepers, have succeeded in creating a buffer zone between the two sides and to bring the situation to an end."

The fighting around Malakal airport was sparked on Thursday when loyalists of Gabriel Tang, who commanded a pro-Khartoum militia during the 1983-2005 civil war between north and south, objected to surrendering their heavy weaponry.

The former militiamen are deployed alongside regular northern troops in so-called Joint Integrated Units with southern forces that patrol the town under the peace agreement that ended the civil war.

In reality the units are far from integrated and the component elements effectively operate as separate forces.

The northern troops are shifting their equipment back home as the south gears up for its expected international recognition as an independent state in July following its overwhelming vote for secession in last month's landmark referendum.

But the ex-militiamen, whose roots are in the south, want to keep their unit's tanks in Malakal and they put up a ferocious resistance to their redeployment.

Six civilians and one SPLA soldier were killed in the crossfire, as the southern force tried to intervene, Aguer said. Two of the dead were young children, he added.

Six regular northern troops and seven former militiamen were also killed in the fighting, Aguer said.

Two civilians and a total of 22 members of the northern force were wounded.