Pope Benedict XVI denounced the profit-at-all-cost mentality that he says is behind Europe's current economic crisis as he arrived in hard-hit Spain on Thursday, and said morals and ethics must play a greater role in formulating economic policy in the future.

Benedict made the comments as he traveled to Madrid for the Catholic Church's World Youth Day, a weeklong Catholic festival that is taking place against a backdrop of the European debt crisis and social unrest among the young that exploded recently in the riots in Britain.

Benedict said the crisis and sense of desperation among young people proved that ethics have been increasingly left out of formulating economic policy at local and international levels.

"The economy doesn't function with market self-regulation but needs an ethical reason to work for mankind," he told reporters traveling aboard the papal plane. "Man must be at the center of the economy, and the economy cannot be measured only by maximization of profit but rather according to the common good."

He said the current crisis shows that a moral dimension isn't "exterior" to economic problems but "interior and fundamental."

Benedict explored the theme more fully in his 2009 encyclical "Charity in Truth," in which he called for a new world financial order guided by ethics, dignity and the search for the common good.

Benedict arrived in a cloudy Madrid to a boisterous welcome from young people with their faces painted the colors of the Spanish flag chanting: "These are the pope's young people!" A cordon of youngsters decked out in faux Swiss Guard uniforms greeted Benedict on the tarmac at Madrid's Barajas airport, along with Spain's King Juan Carlos and Queen Sofia.

Socialist Prime Minister Jose Luis Rodriguez Zapatero and conservative opposition leader Marian Rajoy, the man forecast to take power in November elections, also were present.

Clouds and a breeze kept Madrid's notoriously hot August temperatures down to a relatively comfortable 25 Celsius (77 Fahrenheit), though the mercury inched up as the sun broke through.

In a speech delivered on the tarmac in Spanish, Benedict referred to the precariousness many young people see in their future. Unemployment in Spain is nearly 21 percent and is the highest in the eurozone.

"Many young people look worriedly to the future, as they search for work, either because they have lost their job or because the one they have is precarious or uncertain," Benedict said. He urged young people to keep fast in their faith.

"With God beside them, they will posses light to walk by and reasons to hope, unrestrained before their highest ideals, which will motivate their generous commitment to build a society where human dignity and true brotherhood are respected," he said.

King Juan Carlos also referred to the sense of hopelessness many young people feel, saying today's youth are "frustrated by the lack of personal and work possibilities, and rebel against the serious problems facing the world today."

As Benedict was being driven from Madrid's airport to the Vatican Embassy through one of the capital's ritziest neighborhoods, streets and bridges were filled with youths waving flags, throwing white and yellow balloons _ the Vatican's colors _ and cheering. The popemobile was surrounded by security cars and motorcycles with blue lights flashing.

Later Thursday he is to be officially greeted by World Youth Day participants in Madrid's Plaza de Cibeles.

This is Benedict's third trip to Spain as pope, cementing its reputation as ground zero in his campaign to reinvigorate the faith in European countries where Catholicism has fallen by the wayside. Laws passed under Zapatero allowing gay marriage, fast-track divorce and easier abortions have deeply angered the Vatican, which sees the once staunchly Roman Catholic country as a battleground for the future of the faithful in Europe.

Many Spaniards have balked at the cost of the visit at a time of economic difficulty. Many have cited the fact that pilgrims are getting deeply discounted subway and bus tickets with their accreditation packages, while such prices for everyone else went up 50 percent this month to $1.50.

Vatican Radio responded to the critics Thursday, noting that the euro50 million ($72 million) tab for staging World Youth Day is being paid for by the participants themselves, some private donors and the church. Critics say the organizers' estimate for the price tag doesn't include security costs and is a fraction of the total price tag for Spaniards.

Hours before the pontiff's arrival, riot police and protesters opposed to his stay clashed in downtown Madrid. Police said eight demonstrators were arrested and 11 people were injured in the disturbances Wednesday night in the city's Puerta del Sol plaza.

"People were going really crazy but, at the same time, God wants all of us to be here and I know that he'll like protect us all while we're here," said Holly Springfield, a 17-year-old American who witnessed the protest.

On Tuesday, police arrested a chemistry student working as a volunteer for the pope's visit on suspicion he was planning a gas attack on protesters opposed to the pontiff's visit, officials said. The 24-year-old Mexican student, Jose Perez Bautista from Puebla state, was ordered released on Thursday. He wasn't formally charged but remains under investigation with his passport seized.

Organizers expect a million or more young people from 193 countries to attend the festival.

The main events are a prayer vigil with the 84-year-old Pope and outdoor sleepover for pilgrims Saturday night at a sprawling air base, and Mass there the next morning.

Except for a trip Friday to a historic monastery in El Escorial, 50 kilometers (30 miles) northwest of Madrid, the pope will spend the whole visit in Madrid, meeting with young people, hearing confession from some of them, riding through the city in his popemobile and greeting young nuns, seminarians and university professors, among other activities.

In Spain the church faces a congregation for whom being Catholic is more a birthmark than a way of life. A poll released in July says that while 72 percent of Spaniards identify themselves as Catholic, 60 percent say they "almost never" go to Mass and only 13 percent every Sunday.

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Daniel Woolls and Iain Sullivan contributed.