* Unions protest steel mill closures in Europe
* 24-hour strikes announced in Luxembourg and at Florange plant in France
* Unions: 40,000 demonstrators protest plant closures in Liege, Belgium
By Stefano Ambrogi and Robert-Jan Bartunek
LONDON/BRUSSELS, Dec 7 (Reuters) - Thousands of workers were staging strikes and demonstrations on Wednesday at European plants of ArcelorMittal, the world's largest steelmaker, in what unions said was a protest against job insecurity.
The European Metalworkers Federation (EMF) said strikes ranging from two hours per shift to a 24-hour walkout would take place at plants in Belgium, France and Luxembourg, with stoppages also expected in Italy, Spain and at some sites in Germany. Sites in Poland and the Czech Republic were also expected to suffer some disruption, it said.
ArcelorMittal said 24-hour production halts were limited to plants in Luxembourg, Belgium and one in France but had no major impact on output, as furnaces at most of the sites affected had already been partially idled.
"(The furnaces at) Rodange and Schifflange are idled anyway, Liege is idled, as you know, and so is Florange idled, the furnaces at all these plants are idled," an ArcelorMittal spokesman said.
But at a news conference in London close to the firm's corporate finance offices in the well-heeled district of Mayfair, EMF deputy general secretary Bart Samyn said more than 25,000 workers had walked out, hitting production by at least 10-20 percent across Europe.
Samyn, who represents 72 labour organisations and 95 percent of metal unions in Europe, accused ArcelorMittal of pursuing an irresponsible strategy of rationalisation that could see steel production disappear entirely from the continent.
He said the company was behaving more like "an investment bank than a steel producer" by putting profits before long-term investment in the industry and its skilled workforce.
"We do understand the issues surrounding the problems of the current economic crisis ... but we don't see a strategy in ArcelorMittal, that will keep steel production alive in Europe," Samyn told reporters.
"In the end we could see the disappearance out of most of the countries in Europe, simply making quantity steel in the rest of the world and losing their crown jewels of the past."
Samyn said unions will decide their next course of action, which could include more strikes, following a meeting with management in mid-January over the concerns they have raised.
Belgian unions said there were 40,000 people at a demonstration in the town of Liege on Wednesday.
"There are not just steelworkers here today, there are also workers from other sectors, both industry and services, who are on strike," Eric de Deyn, spokesman for the BBTK union said.
"All shops in the city centre are closed out of solidarity with the workers of ArcelorMittal."
The company announced in October that it would permanently end liquid-phase steel production at its site in Liege, given over-capacity and a slow recovery in the European market.
The group also idled blast furnaces in Florange in France and Eisenhuettenstadt in Germany.
The steel producer, which makes between 6 and 7 percent of global steel and has been laying off staff at some plants, said in early November that a summer dip in demand was deepening into a second-half slump and that customers were increasingly cautious because of economic uncertainties.