Tens of thousands of General Motors employees in Europe are taking part in protests at plans to cut 12,000 jobs.

The BBC said that workers at the Opel unit in Bochum in Germany walked out for a sixth day on Tuesday, while protests are underway at other GM plants in Europe.

Workers at GM plants in Britain - where 400 jobs are to be cut - are also expected to suspend operations briefly.

GM has started negotiating with unions over the job cuts, the report noted.

GM Europe, having failed to make a profit in the last four years, wants to cut costs at the division by as much as €500 million ($US623.8 million; £347 million).

The German newspaper Frankfurter Allgemeine Zeitung reportedly said that GM is determined to press ahead with the cost saving measures, despite the threat of widening strike action.

Opel plant in Ruesselsheim, Germany, has stopped production due to a parts shortage and to workers participating in the Europe-wide protests, an Opel spokeswoman told the BBC. Some 2,500 workers are expected to lay down tools at the factory in Kaiserslautern.

GM said 20-minute breaks were being organised at a factory in Antwerp, Belgium, so workers could attend "information rallies".

Poland's Solidarity union declared a day of solidarity without any stoppages at the Opel factory in Poland.

Meanwhile, at least 10,000 people were expected to attend a rally in protest at the job cuts in Bochum.

Vauxhall supporters in the UK are expected to lend their support, but it is not yet clear what action they will take, the BBC said.

The secretary general of the European Metal Workers Federation, Reinhard Kuhlmann, estimated that altogether about 50,000 workers were taking part in the Europe-wide protests.

Although the firm has not yet said which of its 11 European plants will be affected, GM's German sites appear most vulnerable because of high labour costs, the report noted.

Germany has the second-highest labour costs in the world, according to the Organisation for Economic Cooperation and Development (OECD).

And of the German facilities, staff at Bochum, which makes Astra and Zafira models, look the most at risk after GM recently said the plant had a "competitiveness issue".

Opel works council chairman Klaus Franz told the BBC at the weekend at the weekend that he hoped to convince GM that it could bail out Opel without resorting to layoffs.

Franz reportedly also warned that any ongoing stoppage at Bochum could affect GM's other European facilities, because of the plant's production of some key parts for other GM vehicles.