Two people have died in violence at a Chinese-run sugar refinery in western Madagascar, the country's prime minister said Thursday.

"There are two dead and a part of the refinery has been destroyed," said Roger Kolo.

The unrest appears to have been sparked by a dispute over wages and contracts for local seasonal workers and Chinese managers.

Police intelligence director Anthony Rakotoarisoa said there had been tensions at the Sucoma plant between Malagasy staff and bosses.

Previous clashes have led to "acts of vandalism and physical attacks on the Chinese."

In November two Chinese were injured and property damaged.

The identity of the two people killed, and how they died, was unclear, but Rakotoarisoa said the Chinese staff had been evacuated before the deaths.

Tensions at the plant appear to have increased when two senior labour figures were arrested during a police crackdown Wednesday.

Workers, armed with knives and at least one shotgun, responded by trying to free their leaders.

The security forces said they retreated and fired shots into the air.

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