Reports say the ship is carrying millions of rounds of ammunition
The ship carrying weapons to Zimbabwe may return to China after being prevented from unloading in South Africa, a Chinese official has said.
Zambia's president has called on other African countries not to let the ship enter their waters, in case the arms escalate post-election tensions.
Chinese Foreign Ministry spokeswoman Jiang Yu said the weapons were ordered last year and were "perfectly normal".
But she said the ship's owners were considering bringing the ship back.
Ms Jiang said this was because it was proving impossible for Zimbabwe to receive the arms but this has not been confirmed by the Chinese shipping company.
The Chinese vessel was said to be bound for Angola but the US is reported to be pressuring port authorities there and in Namibia not to allow them to dock.
Zambia's President Levy Mwanawasa said: "I hope this will be the case with all the countries because we don't want a situation which will escalate the [tension] in Zimbabwe more than what it is."
I don't understand all this hullabaloo about a lone ship
Patrick Chinamasa Zimbabwe justice minister
The International Transport Workers Federation says it has asked its members across Africa not to help unload the An Yue Jiang, which is reportedly carrying three million rounds of ammunition, 1,500 rocket-propelled grenades and 2,500 mortar rounds.
The opposition says the weapons could be used to "wage war" on its supporters ahead of a possible run-off in the presidential vote.
This is strongly denied by the government, which has accused the opposition of exaggerating claims of recent political violence.
The ship, which had been anchored off the port of Durban for four days, was forced to move on Friday after a South African court refused to allow the weapons on board to be transported across the country to landlocked Zimbabwe.
Despite reports the ship was heading for Angola, an ally of Zimbabwe's government, the director of the Institute of Angolan Ports said the vessel had not asked for permission to dock in Angola.
"This ship has not sought request to enter Angolan territorial waters and it's not authorised to enter Angolan ports," Filomeno Mendonca told local radio.
But the agent handling the ship said its next port of call would be the Angolan capital, Luanda, AFP news agency reports.
A South African military spokesman said the ship was no longer in South African waters.
Zimbabwe's Justice Minister Patrick Chinamasa said it was their right to defend themselves and buy weapons from any legitimate source.
"I don't understand all this hullabaloo about a lone ship," he told reporters.
The country has yet to publish the results of its 29 March presidential election, which the opposition Movement for Democratic Change (MDC) says was won outright by its candidate Morgan Tsvangirai.
Meanwhile, the southern African regional body, SADC, rejected Mr Tsvangirai's calls for South Africa's Thabo Mbeki to be replaced as the chief mediator for Zimbabwe.
"We have complete faith in President [Thabo] Mbeki," AFP quoted Mauritius Prime Minister Navin Ramgoolam as saying.
Mr Tsvangirai wants President Mwanawasa to take over, with some opposition supporters saying Mr Mbeki was close to Mr Mugabe.
A Chinese arms ship heads for the African coast on its mission to deliver weapons to Zimbabwe
A recount in 23 out of 210 parliamentary seats, which had been due to end on Monday, has been delayed for an unknown period.
The MDC rejected the recount as illegal and insisted it beat President Robert Mugabe's Zanu-PF party outright in presidential and parliamentary polls.
The leader of the governing African National Congress in South Africa - Jacob Zuma - has again criticised the delays in publishing the election results - further distancing himself from Mr Mbeki.
"It's not acceptable. It's not helping the Zimbabwean people who have gone out to ... elect the kind of party and presidential candidate they want, exercising their constitutional right," he told Reuters news agency.
He called on African leaders to take action to solve the political deadlock that has set in since last month's disputed election.
Post-election violence has displaced 3,000 people, injured 500 and left 10 dead, according to MDC secretary general Tendai Biti.
All the signs are that the ruling Zanu-PF party is still deeply split over how to handle the crisis
Human rights groups say they have found camps where people are being tortured for having voted "the wrong way".
But Mr Chinamasa denied that anyone had died in political violence.
Police spokesman Wayne Bvudzijena said that of the 10 people reported dead, only four names had been supplied and "of these three no basis whatsoever while the fourth is still under investigation and will be concluded soon", he was reported as saying by the state-owned Herald newspaper.
Zimbabwe's church leaders are also calling for intervention to prevent the violence reaching genocidal proportions.
"If nothing is done to help the people of Zimbabwe from their predicament, we shall soon be witnessing genocide similar to that experienced in Kenya, Rwanda, Burundi and other hot spots in Africa and elsewhere," leaders of the main denominations said in a joint statement.
"We appeal to the Southern African Development Community (SADC), the African Union and the United Nations to work towards arresting the deteriorating political and security situation in Zimbabwe," a statement said.
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