Reports say the ship is carrying millions of rounds of ammunition
Zambian President Levy Mwanawasa has urged other African leaders not to allow a ship carrying arms for Zimbabwe to enter their territorial waters.
Mr Mwanawasa said the tension in Zimbabwe, following last month's disputed elections, should not be allowed to escalate further.
Zimbabwe's justice minister said it was their right to defend themselves and buy weapons from any legitimate source.
The ship has already been turned away from South Africa and Mozambique.
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.
Even people who have died of natural causes are adopted by the MDC-T
Patrick Chinamasa Zimbabwe justice minister
"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," said Mr Mwanawasa.
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, director of the Institute of Angolan Ports Filomeno Mendonca 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," he told local radio.
A South African military spokesman has said the ship was no longer in South African waters.
South African Defence Ministry spokesperson Themba Gadebe was speaking in response to a claim that the ship remained in the country's jurisdiction despite last week's court order.
The Southern Africa Litigation Centre (Salc), which took the matter to court, had asked the South African navy to intervene.
Mr Gadebe said the ship was being monitored but declined to say where it was, except that it was off South Africa's west coast.
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 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, has 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 Mbeki," the AFP news agency quotes Mauritius Prime Minister Navin Ramgoolam as saying.
Mr Tsvangirai has wanted President Mwanawasa to take over, with some opposition supporters saying Mr Mbeki was close to Mr Mugabe.
A recount in 23 out of 210 parliamentary seats, which had been due to end on Monday, was delayed for an unknown period.
The MDC has rejected the recount as illegal and insists it beat President Robert Mugabe's Zanu-PF party outright in the 29 March presidential and parliamentary polls.
Secretly filmed footage of alleged attack victims in Zimbabwe
Post-election violence has displaced 3,000 people, injured 500 and left 10 dead, according to MDC secretary general Tendai Biti.
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.
"Even people who have died of natural causes are adopted by the MDC (Tsvangirai) and the cause of death is subsequently attributed to state-sponsored violence," he said.
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.
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