Thousands of workers at three Volkswagen factories staged protest demonstrations on Tuesday to turn up the pressure on management ahead of a crucial round of wage talks later this week.

The powerful IG Metall labour union told Agence France-Presse (AFP) that around 3,500 workers attended a demonstration at VW’s engine factory in Salzgitter in northern Germany. Nearly 3,500 workers joined in protests at another north German factory in Emden, where the car maker assembles its mid-range Passat, and protests were also staged in VW’s home town of Wolfsburg.

AFP noted that the demonstrations come just two days before management and unions at Europe’s biggest car maker are scheduled to return to the negotiating table for a key fifth round of talks to discuss VW’s draconian cost-cutting plans.

While no major advances were made in previous rounds, talks this week were likely to prove crucial because Thursday is the date when both VW’s current wage agreement and the so-called “Friedenspflicht” deadline banning industrial action during wage negotiations are scheduled to expire, the report added.

IG Metall has threatened to stage warning strikes in the beginning of November if no deal is reached on Thursday.

Agence France-Presse said VW is seeking a two-year wage freeze for the 103,000 staff on German assembly lines and a 30% reduction in labour costs by 2011.

IG Metall, for its part, is demanding job guarantees for 10 years and a 4% increase in wages. But it has signalled it is willing to review its demand for higher wages if it can obtain an “acceptable” solution with regard to the job guarantees.

However, management has rejected the proposals, which it argues would generate new costs for VW’s German manufacturing sites, Agence France-Presse said.