Thousands of protesters marched against a planned high-speed train line in northern Italy on Sunday as police turned out in force fearing rioting by militants and hooligans. Hundreds of women led the peaceful procession from Giaglione to a construction site in the Susa Valley near Turin, wielding wire-cutters aimed at gaining access to the site. But their hopes of doing so were thwarted by some 1,700 Italian security forces encircling the site at a wide radius, acting on a threat Saturday by anarchists and other hardcore militants to join the protest. Organisers instructed the protesters not to provoke the police. \"This demonstration is determined but peaceful,\" a \"No TAV\" organiser told the protesters as the march set off. \"Those with wire cutters will cut the wire and immediately turn their backs on the police officers and leave,\" he said, adding: \"We don\'t want to see helmets, gas masks or blunt instruments.\" Organisers put the number of protesters at 20,000, though local police said there were no more than 700. Chanting slogans and waving banners, the protesters cut through a first wire fence while police looked on, but were unable to get through a second robust barrier and set off through the surrounding woods to find another route. No clashes were reported between police and protesters. Seven youths were taken into custody early Sunday after being found in the off-limits area with motorcycle helmets and gas masks. Another five people were taken aside for questioning at the start of the morning\'s march. France and Italy signed a deal in 2001 on building a high-speed (TAV) line through the Susa Valley area, a strategic link in the European network that would cut travel time between Milan and Paris from seven to four hours. The cost has been estimated at 15 billion euros ($21 billion). But Susa Valley residents fiercely oppose the plan, saying the construction of tunnels would damage the environment. Protests by the No TAV movement have been infiltrated by violent activists in the past, and militants who led riots in Rome last weekend which left 135 people injured had threatened to join the rally. On a message on their website, the Federation of Anarchists in Turin said they planned to attend, declaring they were \"not afraid of police violence, of persecution in the media, or of being arrested.\" If security forces tried to challenge the group, \"they will have to choose between shooting us or backing off,\" the anarchists said. Police on Saturday arrested a 23-year-old who was heading to Turin to the demonstration and charged him with attempted murder after he was identified as having assaulted officers and set a police van ablaze in the Rome riots.