MILAN — The Expo 2015 world's fair showed potential as a backdrop for serious diplomacy as it opened Friday for a six-month run, even as it also served as a lightning rod for anti-globalization protests.
North Korea stepped out of its isolation as a last-minute participant, and there are signs that Turkey may use the occasion to reach out to the Vatican weeks after it recalled its ambassador to the Holy See over the pope describing the slaughter of Armenians by Ottoman Turks as genocide.
With food as the theme of this year's event, culinary delights from host Italy and beyond will be one of the main draws for the fair's hoped-for 20 million visitors. But the Milan Expo already had greater ambitions, with the Italian government backing a process to create a document of solutions to fight hunger and food waste, among other goals.
A violent protest Friday, however, left torched cars, smashed bank and shop windows and other damage in the streets of downtown Milan, far from Expo's sprawling grounds on the financial capital's outskirts. Protesters split off from a generally non-violent march a few hours after Italian Premier Matteo Renzi inaugurated the fair.
Police fired tear gas and sprayed water after protesters, many wearing scarves or hoods to mask their faces, tossed bottles and incendiary devices, set cars and garbage bins afire and smashed pavement. Firefighters worked to extinguish the blazes. Milan police said 11 officers were injured and that an unspecified number of protesters were detained.
Some marchers' placards protested a high-speed rail line being built in northern Italy as well as Expo 2015 and other "big projects."
With millions of visitors expected to come to Milan for Expo in the coming months, Milan Mayor Giuliano Pisapia said "the delinquents devastating Milan (will) be isolated, identified and punished" without exception.
Bracing for any more violence, police presided over intersections leading to Milan's La Scala opera house, where "Turandot," with a VIP audience, was on the program Friday evening. Only theater workers and those with tickets were being allowed to approach the theater.
In a peaceful protest Thursday by students, participants opposed the inclusion of food corporations like Coca Cola, Nestle and McDonald's in the fair. Protester Selam Tesfai said those companies don't adhere to the Expo's slogans of "feeding the planet" and "energy for life."
"They only gonna to try to make profits on our lives and we are tired of that," she said.
Pope Francis hailed Expo's hunger-fighting goals in a speech Friday delivered by video from Vatican City to a VIP audience at the Expo's inauguration, speaking of the "millions of people who are hungry today, who don't eat today in a way worthy of a human being."
"I'd want every person, starting today, who visits the Expo in Milan, passing through these marvelous pavilions, to be able to feel the presence of those faces," Francis said.
The ambition of the "Milan Charter" is to get individuals, civil groups and businesses to back a series of solutions to hunger, a diplomatic trend that recognizes that some problems are too vast for governments alone to resolve.
"What the Italians are doing with this international exposition is creating a global platform that brings the representatives of 145 countries together convening around a key topic, that is food and food security, and the question of how to feed 9 billion people," said Philip T. Reeker, the U.S. consul general in Milan.
He called it "the essence of public diplomacy" focused on "a policy question that concerns us all."
Still, the Expo could also host more than soft diplomacy.
The Vatican's top culture official, Cardinal Gianfranco Ravasi, welcomed the prospect of an invitation to the Turkish pavilion, and extended his own to Turkish officials to visit the Vatican pavilion "dedicated to themes that can be shared also by the Muslim world." He cited spiritual and physical hunger, charity and fasting.
The addition of North Korea just weeks before the Expo's opening was unexpected. Expo officials included the isolationist nation in a thematic cluster dedicated to islands — more metaphorically than geographically apt. Just what form North Korea's participation in Expo will take wasn't clear because that cluster of pavilions wasn't complete yet.
The U.N. food aid agency began giving North Korea food in the 1990s. Some opponents say this and other aid was siphoned off to North Korea's military and nuclear weapons programs, benefiting the elite and easing pressures on the country's rulers to face North Korea's economic problems.
Not all of the diplomatic signals around Expo have been positive. India, in a drawn-out dispute with Italy over its determination to put two Italian sailors on trial for the shooting deaths at sea of two fishermen, skipped the global event due to the tensions, Expo organizers said.
While the Milan Charter may bring progress on the theme of food security, former Italian diplomat Sergio Romano cautioned against expecting any political breakthroughs on the sidelines.
"Expo, I think, cannot produce any policy whatsoever because it isn't their job. What it can do is get people to the same place with all the possible advantages it can create," said Romano. "It would be wrong to try to produce political results, because it is basically an economic exhibit."
Paolo Santalucia contributed to this report.