Beijing - China said on Tuesday a shipment of weapons bound for Zimbabwe might head back after the vessel was unable to unload, but defended the cargo as "perfectly normal trade".

Zambia's president urged regional states on Monday to bar the An Yue Jiang from entering their waters, saying the weapons could deepen Zimbabwe's election crisis. The ship already failed to unload its cargo in South Africa, Mozambique and Angola had denied it access to their ports.

Chinese Foreign Ministry spokesperson Jiang Yu said the contract for the shipment was signed last year and was "unrelated to recent developments" in Zimbabwe.

Jiang said the arms shipment was "perfectly normal trade in military goods between China and Zimbabwe", but because it was impossible for Zimbabwe to receive the goods, the company involved was now considering shipping the cargo back.

Zimbabwe announced a delay on Sunday in a partial recount of votes in March 29 elections, extending a deadlock in which the opposition said 10 of its members had been killed and hundreds arrested.