UPDATE 4-GM's U-turn on Opel sale angers Germany, Russia

* German Economy Minister says GM behaviour "unacceptable"

* Russia's Putin says GM should not have final word

* Opel labour leader rescinds cost-cut contributions

* Opel to implement GM board decision quickly

(Adds comments from EU, Britain, Opel workers)

By Angelika Gruber and Gernot Heller

FRANKFURT/BERLIN, Nov 4 (Reuters) - German and Russian leaders seethed and unions tore up a deal to cut costs in protest at General Motors' [GM.UL] "completely unacceptable" decision to keep Opel, its European unit, after months of talks.

Labour leader Klaus Franz rescinded hundreds of millions of euros in cost concessions that workers agreed to on condition that Opel was bought by Magna (MGa.TO: Quote, Profile, Research), the Russian-backed Canadian group long backed as buyer by Berlin and Moscow.

"General Motors' behaviour towards workers is completely unacceptable," German Economy Minister Rainer Bruederle told reporters the morning after GM's shock news, adding: "General Motors' behaviour towards Germany is completely unacceptable."