SEOUL: Thousands of riot police on Monday strengthened their siege of a troubled South Korean auto firm, spraying liquid tear gas from a helicopter, after talks to end a prolonged occupation by strikers collapsed.

Television showed police with helmets and shields moving closer to a paint shop at the Ssangyong Motor plant in Pyeongtaek, 70 kilometres (43 miles) south of Seoul.

On Sunday, three days of talks between managers and union leaders broke down, raising concerns the embattled company may go bankrupt.

"Today, police strengthened their force in and around the plant, from 3,000 to 4,000," company spokesman Cha Ki-Ung told AFP.

Hundreds of workers, armed with metal pipes, powerful slingshots and inflammable paint thinner, have occupied the factory since May 21 in protest at job cuts designed to save the Chinese-invested company.

Police moved in on July 20 and took over some buildings, but strikers have held out in a barricaded paint shop stacked with inflammable materials.

There have been no hand-to-hand clashes, but dozens of people have been injured as strikers fired nuts and bolts from the slingshots. Management has cut off water and power supplies to the paint shop.

The debt-stricken firm in February secured court protection from creditors after China's Shanghai Automotive Industry gave up management control.

Court-appointed managers have since struggled to turn it around through job cuts and cost savings.

The programme calls for the sacking of 2,646 workers or 36 per cent of the workforce. Some 1,670 of these have taken voluntary retirement, but the others began an occupation of the plant.

As of early Monday, fewer than 600 unionists were still holed up inside the paint shop, Cha said, after about 100 more of them gave up the occupation.

"There will be more deserters who are tired and do not want the plant to be closed," he said.

Creditors have threatened to push for bankruptcy against the loss-making plant. But the union has refused to give up its demands for no layoffs and no lawsuits against it for damages.

The standoff has cost about 300 billion won (244 million dollars) in lost revenue. The country's smallest auto firm specialises in sport-utility vehicles and luxury sedans.

- AFP/so