Thousands of students, parents and teachers took to the streets of this capital and other Spanish cities on Thursday to defend the principle of free, quality public education.

It was the eighth protest of its kind in Spain since September, when the government of the Madrid region announced a plan to increase teachers' working hours and lay off 3,300 interim instructors.

Teachers union say that as many as 50,000 interim instructors could lose their jobs if the Madrid approach were adopted nationwide.

Here in the capital, the ranks of the marchers in the capital were swelled by students from six publicly supported Madrid universities.

Around 250 students from Complutense University blocked traffic for 30 minutes on a highway near Moncloa Palace, seat of the Spanish government, to protest cuts in education spending.

The protest in the southern city of Seville featured the reading of a manifesto proclaiming that students are not responsible for the global economic crisis.

Barcelona, Spain's second-largest city, saw a sit-in and march by some 10,000 people who shut down traffic in part of the downtown area.

The demonstrations come three days ahead of early general elections in which the conservative main opposition Popular Party is expected to defeat the governing Socialists.

Pressure from the financial markets and the European Union has prompted Spain to adopt austerity policies even as the country suffers with an unemployment rate of 21.5 percent.