Spanish trade unions say an estimated 10 million people followed their call for a general strike on Thursday.

At the end of the 24-hour stoppage, union leaders told a big rally in Madrid that there would be further action if the government did not back down over changes that tightened unemployment benefits.

Unemployment law changes

No benefits if unemployed don't take one of first three "acceptable" job offers Reduced benefits for casual farm labourers No salary during appeals against dismissal Spain's unemployment rate of 11.5% is highest in EU

The one-day strike - the first in nearly a decade - was aimed at causing maximum embarrassment for conservative Prime Minister Jose Maria Aznar ahead of the EU summit in Seville on Friday.

But the government insists the reforms are essential to ensure that Spain can keep up with competition and provide an open and flexible labour market

The two main unions involved, UGT and Comisiones Obreras, said more than 80% of employees had stayed away from work.

The government maintained that the majority of Spanish citizens had gone to work as usual and poured scorn on the term general strike.

In Seville airport, bus and train terminals were deserted leaving tourists and locals stranded.

Riot police guard the Corte Ingles department store in Madrid

National airline Iberia said 80% of its flights on Thursday had been cancelled. All long-distance trains were cancelled by national rail company RENFE.

The Madrid metro system ran with about half its normal number of trains, and two-thirds of the 1,000-plus daily arrivals and departures at Madrid's Barajas airport were cancelled.

One stranded Brazilian tourist told the BBC's World Service: "I arrived here in Barajas at one thirty in the morning.

"I came from London and I had a connection here to go to Brazil so I lost a flight that was supposed to leave here at half past midnight.

It was the second day of chaos for air travellers around Europe after another strike by French air traffic controllers on Wednesday.

Shoppers frightened

In the normally bustling shopping streets around the Puerta del Sol in Madrid, many stores were closed.

Strikers tussle with a skinhead in Valencia

Outside the Corte Ingles department store, riot police with black helmets and truncheons stood guard at the front door to fend off a crowd of whistle-blowing strikers.

The protesters screamed obscenities at anyone who entered or left the store and called them scabs. Frightened shoppers scurried away.

In other reports, union members on picket lines prevented employees in cars from reaching work, or filled the locks of factories with silicone to prevent other staff from opening up for business.

At least 63 strikers were arrested nationwide, the interior ministry said.

The strike posed the stiffest challenge from unions since Mr Aznar took power in 1996.

The government's unemployment reform, which the government passed by decree last week, would eliminate salary payments made to Spanish workers who have been fired and are appealing in court.

It would also curtail payments to temporary farm workers and cut off payments to unemployed people who repeatedly snub jobs the government finds for them.