Katya Adler The BBC's Spain correspondent at Atocha station in Madrid

Once again, as after the 11 of March Madrid bombings, people are reluctant to use public transport in the capital. Many feel the risk is just too great to take.

Life had begun to get back to normal.

It is just over three weeks since the attack at Madrid's Atocha station, which left 191 people dead.

You still saw black ribbons of mourning hanging in shops, cafes and even car windows. The ad hoc shrines to the victims, of candles, flowers and hand written prayers, were still being maintained at the Madrid station.

Vigils to the bomb victims are still being held in Madrid

But on the whole, people felt the worst was over.

Then came the news that explosives had been found on a high speed train line on Friday. It has shocked people, once again, to the core.

The newspaper La Razon, commented, "Our enemies know us well and how best to hurt us the most".

The 11 March train attacks were timed to explode at the height of the rush hour. This second attempt coincided with the beginning of the Easter holiday.

If people really want to cause another bloodbath, eventually they will find a way. What can you do? Certainly not lock yourself up forever Train passenger

A reported 23 million Spaniards were on the move when the bomb attempt was foiled, a large proportion of them travelling in crowded trains.

Many in Spain have already made up their minds as to who was responsible.

El Mundo, a daily newspaper, blames "Islamic terrorists". They say police sources have told them one radical Moroccan combatant group was behind both operations.

Angel Acebes, the country's acting interior minister, says it is too early yet to say who was responsible, even though the type of explosives used in both instances were the same. He has asked the public not to panic and to have confidence in the authorities.

New security measures have been introduced to monitor train services across the country. These include army helicopters, sniffer dog teams and armoured vehicles. But extra security measures were already in place following the 11 March bomb attacks.

The explosives found on Friday were on the train line that runs between Seville and Madrid.

Defiance

I spoke to one young man as he boarded a train in Madrid with his three young children.

"No matter what measures are implemented by the government," he said. "If people really want to cause another bloodbath, eventually they will find a way. What can you do? Certainly not lock yourself up forever."

Thousands turned out in protest after the 11 March bomb attacks

Scared but defiant is probably the best way to describe the mood in Madrid. People are un-nerved at the apparent ease with which the would-be attackers were able to plant the explosives on Friday.

But most are determined not to give in.

I approached one woman who was weighed down with flowers and Easter eggs. She was on her way to visit her family in Seville.

"We Spaniards have lived with Basque separatist violence for over 30 years" she said.