The French government said Sunday it was worried about a `sabotage` campaign after another attack severely disrupted the country`s rail network, long seen as one of the most efficient in the world.

`That alas is the reality,` said Transport Minister Dominique Bussereau when asked on French radio if the acts of vandalism might be the result of organised sabotage, adding that police had been instructed to be extra vigilant.

His comments came a day after thousands of French rail passengers suffered long delays or cancellations in the north and east of the country after high-speed rail lines were attacked.

Vandals jammed iron bars into overhead power electricity cables in four separate locations, leaving hundreds of passengers stranded for hours in trains and thousands more crowded into stations trying to get on delayed trains.

Railway officials said that it was the fourth time in three weeks that `malicious acts, even sabotage` had hit the railways.

The high-speed line from Paris to the north was worst hit, with Eurostar services to Britain and Thalys services to Brussels and northern Europe, as well as trains to northern France, badly affected.

The networks serving the east and southeast were also hit. In all, 160 services were affected with delays lasting between 10 minutes and more than four hours.

Interior Minister Michele Alliot-Marie has ordered a top-level inquiry into the incidents.

Services had already been disrupted by the discovery of the mutilated body of a man on the main line to the north.

France`s normally efficient and punctual rail network is a source of national pride. But in recent months it has been hit with a series of high-profile incidents, some caused by infrastructure problems but several by apparent vandalism.

Just a week ago, the SNCF said that gun shots had severed an overhead cable on the line of a high-speed TGV train in the Paris region, severely disrupting traffic for 50 trains.

In a separate problem, Eurostar trains between London, Paris and Brussels have been disrupted since September 11 after a fire in the cross-Channel tunnel injured several people and shut one of the two undersea rail lines.

Disruption due to infrastructure problems in recent months has angered passengers, and on Monday Transport Minister Bussereau said the government would more than double investment in the rail network to reach 13 billion euros (17 billion dollars) by 2015.

Under the programme launched on Monday, the government says it will spend some two billion euros annually up until 2015 to modernise rail infrastructure, more than double the 900 million euros spent in 2007 and 2006.

The new commitment will `create an impetus that will end the vicious cycle of a network caught in degradation,` said Hubert du Mesnil, president of the French RFF rail infrastructure company.