Tens of thousands of people rallied in Madrid on Saturday to protest cuts in education spending imposed by the Socialist government to stabilise the debt-burdened nation's finances.

"For sale -- Public education" read banners hoisted by demonstrators who flocked to Madrid from across Spain following a rally call from a top education union, which said between 70,000 to 100,000 people turned up.

A police estimate was not immediately available.

Protesters, who at times paralysed traffic in the capital city's centre, accused political leaders of "charging education for a crisis it did not create", in a manifesto read by protest organisers at the end of the rally.

Spain is seen by some economists as a weak link the debt-wracked eurozone and has already had its credit rating downgraded by the world's top three ratings agencies.

The Socialist government, which is widely expected to be chased from office in November 20 elections, has imposed big spending cuts in healthcare and education.

Earlier this month, high school students massed in the streets of Madrid and Barcelona, calling for bankers and not students to suffer from cutbacks.

The teachers, parents and students who rallied on Saturday shouted "no to cuts" as they beat drums and blew whistles while marching through the streets during an afternoon protest that remained peaceful.

"What they want to do is privatise education and all public services," said Manuel Pascual, among the many teachers who turned out on Saturday.

Pascual and others said they feared that plans to cut public education spending would only intensify following upcoming elections which would likely be won by the right-of-centre Popular Party, according to opinion polls.

"We are going towards a model where public education will be marginal and only those with money will be able to have access" to quality education said Berta Fernandez, wearing a sign with the word 'grandmother'.

"I have had a temporary contract for 12 years and for the moment it has been renewed," said Jose Antonio Molero, a 40-year-old English teacher for the Extremadura region.

"But I have more and more colleagues who no longer have work and have found themselves unemployed."

Spain's unemployment stands at more than 20 percent, one of the worst rates among industrialised nations.

Because of the cuts, "there are teachers who have to give courses in subjects that are not their own", said Francisco Angel Hernandez Alvarado, a 36-year-old physical science teacher from Spain's Toledo region.

Whichever government emerges from the upcoming election will likely have little room to boost public spending, as the country's economic forecasts remain grim.

The government has officially stuck to its economic growth target of 1.3 percent for 2012, despite warnings by economists that activity is slowing and that instability in Greece, which is nearly bankrupt, could spread to Spain.