LYON, France (Reuters) - Two managers of German electrical and engineering group Siemens AG were released on Tuesday after being held in their offices overnight by employees demanding concessions over job cuts.

Staff representatives said management had refused to bow to their demands for more generous redundancy terms, but they expected negotiations to continue under the mediation of local government officials.

"The two managers have just left the building, booed by the employees," said Georges Boncompain, who is on the works committee at the Siemens unit in southeastern France.

The incident was the latest in a long series of so-called "bossnappings" in which managers in France have been detained by staff to exert pressure in negotiations over wages or lay-offs.

Industry Minister Christian Estrosi condemned the incident and had called on the workers to release the managers, one a human resources executive and the other the financial director.

"There can be no negotiation while there is violence," he told France Inter radio.

Union representatives at Siemens VAI, which produces machines used in the metals industry, have criticized the extent of planned job cuts and also the amount of compensation offered to workers who will lose their job.

Boncompain said the group wanted to cut 240 of the 600 jobs at the site and rejected as "indecent" the compensation offered by the company, which he said was between 5,000 euros ($6,761) and 24,000 euros according to individual cases.

Unions have demanded 30,000-euro payouts.

($1=.7395 Euro)

(Reporting by Catherine Lagrange; Writing by James Mackenzie and Crispian Balmer; Editing by Jon Boyle)