Masked left wing demonstrators set up fire to the Buenos Aires offices of Neuquen State governor Jorge Sobisch, Thursday, April 5, 2007. Demonstrators protested Wednesday against repression to teachers in the city of Neuquen, some 1,200 kms (1933 miles) south west of Buenos Aires, where Carlos Fuentealba, one of the teachers seeking higher pay, was seriously wounded by a tear gas grenade thrown by riot police and died Thursday. Argentina's main teacher's union called for a one-day national strike next Monday.