China's embassy in Madagascar said Saturday it was "very shocked" by a violent labour dispute at a Chinese-run sugar factory in the west of the island that resulted in four deaths this week.

A spokesman at the embassy told AFP in a statement it was "regrettable" that "troublemakers incited by people with bad intentions" were using violence at the Sucoma plant.

The embassy also complained that Malgasy authorities were not upholding a duty to protect the factory.

On Wednesday, clashes between police and Sucoma workers demanding the release of two of their leaders who had been arrested turned deadly, with two people killed and nine wounded. The plant's sugar stocks were also looted.

On Thursday, a policeman and a soldier posted to the factory were slashed to death with knives.

The Malagasy workers at the plant are demanding better wages, and contracts for seasonal workers.

The embassy insisted the Chinese company that owns the plant was respecting local laws, and said it had created many jobs in the town of Morondava.

It said it was up to Madagascar's government to handle the matter so that "negative influences" are not felt on the island's investment climate.

China's vast investment in countries across Africa has led to social unease in some countries, with the visitors sometimes accused of exploiting workers.