Chinese troops have been seen on the streets of Zimbabwe's third largest city, Mutare, according to local witnesses. They were seen patrolling with Zimbabwean soldiers before and during Tuesday's ill-fated general strike called by the opposition Movement for Democratic Change (MDC).

Earlier, 10 Chinese soldiers armed with pistols checked in at the city's Holiday Inn along with 70 Zimbabwean troops.

One eyewitness, who asked not to be named, said: "We've never seen Chinese soldiers in full regalia on our streets before. The entire delegation took 80 rooms from the hotel, 10 for the Chinese and 70 for Zimbabwean soldiers."

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Officially, the Chinese were visiting strategic locations such as border posts, key companies and state institutions, he said. But it is unclear why they were patrolling at such a sensitive time. They were supposed to stay five days, but left after three to travel to Masvingo, in the south.

China's support for President Mugabe's regime has been highlighted by the arrival in South Africa of a ship carrying a large cache of weapons destined for Zimbabwe's armed forces. Dock workers in Durban refused to unload it.

The 300,000-strong South African Transport and Allied Workers Union (Satawu) said it would be "grossly irresponsible" to touch the cargo of ammunition, grenades and mortar rounds on board the Chinese ship An Yue Jiang anchored outside the port.

A Satawu spokesman Randall Howard said: "Our members employed at Durban container terminal will not unload this cargo, neither will any of our members in the truck-driving sector move this cargo by road. South Africa cannot be seen to be facilitating the flow of weapons into Zimbabwe at a time where there is a political dispute and a volatile situation between Zanu-PF and the MDC."

Three million rounds of AK-47 ammunition, 1,500 rocket-propelled grenades and more than 3,000 mortar rounds and mortar tubes are among the cargo on the Chinese ship, according to copies of the inventory published by a South African newspaper.

According to Beeld, the documentation for the shipment was completed on 1 April, three days after the presidential vote.

Zimbabwe and China have close military ties. Three years ago, Mr Mugabe signed extensive trade pacts with the Chinese as part of the "Look East" policy forced on him by his ostracising by Western governments over human rights abuses. The deal gave the Chinese mineral and trade concessions in exchange for economic help.

The shadow Foreign Secretary William Hague called on David Miliband to demand a cessation of arms shipments.

A South African government spokesman Themba Maseko said it would be difficult to stop the shipment.