BRENNER, Austria (Reuters) - A demonstration against a plan to restrict access through the Brenner Pass between Italy and Austria turned violent on Saturday, with Italian police firing teargas at hundreds of protesters throwing stones and firecrackers.

Austria has said it plans to erect a fence at the Alpine crossing it shares with Italy to “channel” people. Part of Europe’s borderless Schengen zone, Brenner is one of the routes that migrants use as they head towards wealthy northern Europe.

Two police officers were injured in the clashes, the head of a local Italian police union, Fulvio Coslovi, told Reuters. He said around 10 demonstrators were being held by police.

Local police in Tyrol, Austria said over 600 protesters showed up to the third violent demonstration at the Brenner Pass in just over a month, meeting at the Brenner station in Italy.

TV footage showed clouds of smoke filling the Brenner railway station as groups of protesters, their faces masked against the fumes, hurled stones and smoke bombs as they faced off against lines of police in riot gear. Estimates on the number of demonstrators varied between 250 and 600.

Around 300 Austrian police officers were deployed but had not yet had to intervene, a spokesman said, since the protest had taken place exclusively on the Italian side of the border so far.

Italian newspaper Corriera della Sera reported earlier this week that the protest had been organized by an anarchist group from Trentino, northern Italy, and was expected to attract demonstrators from abroad.

Austrian Interior Minister Wolfgang Sobotka said in Rome last month that as many as a million migrants were poised to cross the Mediterranean from Libya this year. Italy says the figure is much lower, though calm summer seas may well bring a surge.

Italy and Germany are utterly opposed to Austria’s plan to build a fence at its border with Italy, Italian Prime Minister Matteo Renzi said on Thursday after talks with German Chancellor Angela Merkel.