Nairobi/Khartoum  - Sudan has summoned the ambassadors of Kenya and Ethiopia to register a complaint about "illegal" arms shipments to the semi-autonomous south, the Sudanese embassy in Kenya said Tuesday.

Sudan is angry about a shipment of tanks and other military equipment that was allegedly en route to South Sudan through the Kenyan port of Mombasa before being seized by pirates off the coast of Somalia.

Khartoum also said that weapons arrived in South Sudan's capital Juba on Friday aboard an Ethiopian military plane.

The cargo of 33 T-72 tanks and other equipment aboard the Ukrainian ship MV Faina is still being held by pirates, who are demanding a multi-million-dollar ransom.

The pirates, who are hemmed in by international warships, have threatened to blow up the ship if they do not receive the ransom, which was originally set at 20 million dollars.

Both the pirates and maritime officials have said that the cargo was destined for South Sudan, a charge repeatedly denied by both Kenya and South Sudan.

Kenya has said that the equipment was for use by its own military.

North and South Sudan have maintained a fragile peace since 2005, although recent tensions in the town of Abyei brought the two sides close to war again.

Should the shipment prove to have been headed for South Sudan, the prospects for long-term peace could be dealt another blow.

South Sudan is not subject to an arms embargo, but the terms of the 2005 peace deal forbid the purchase of arms without the joint approval of both states. (dpa)