Trading on Madrid's stock exchange has resumed after a five-hour blackout that was blamed on a technical glitch.

The benchmark Ibex 35 shot up when trading began again just before 3pm. It closed the day 4.4% higher.

The Ibex lists major global companies like Inditex, the owner of the Zara, as well as banking group Santander and telecoms operator Telefonica.

An exchange spokesman, Jesus Merino, said technical problems had caused the breakdown today but he could give no further details.

Spain's stock market has been convulsed in recent months as investors react to the ups and downs of the country's economic crisis. 

The government is desperate to avoid having to seek a sovereign financial bailout but its problems are mounting. Debt is rising due to the cost of rescuing ailing banks and regional governments, while the economy is in recession and unemployment is near 25%.

The economic troubles of Spain and the wider 17-nation euro zone were among the topics discussed by Spanish Prime Minister Mariano Rajoy and US President Barack Obama during a 30-minute call today, Rajoy's office said in a statement.

Rajoy told Obama about Spain's efforts to reduce the government deficit and the series of budget cuts that his administration has pushed through since the beginning of this year.