UNITED NATIONS — International Youth Day was commemorated here Aug. 12 with activities celebrating youth culture in all of its diversity — from Brooklyn to China — as well as more poignant reminders of the desperate situation faced by hundreds of millions of young people around the globe.

“Today, there are almost 3 billion people in the world under the age of 25,” said UN Secretary-General Kofi Annan. “More than half a billion of them live on less than $2 a day. More than 100 million school age children are not in school. Every day almost 30,000 children die of poverty and 7,000 youth become infected with HIV.

“I know you will not accept a world where others die of hunger, remain illiterate and lack human dignity,” Annan continued. “So please make sure your voices are heard. Make sure your generation is the one to defeat poverty.”

Conference organizers emphasized the themes of empowering youth and improving their lives, with special reference to the Millennium Development Goals (MDGs), a set of eight goals all 191 UN member states agreed to reach by 2015. The MDGs, if met, will begin to lessen the poverty and misery that engulfs much of the world’s population.

Basketball star Dikembe Mutombo of the Houston Rockets, who was on hand for a conference-sponsored basketball game with young people from New York City, said that improving education worldwide was necessary to better “the economy, culture and social life” of young people.

“I think there’s chance for all of us, not just the UN, but for all of us, with our intelligence, with our material, with our resources that we have, to reach the goals,” Mutombo told the World. “The goals will not be fulfilled in a day; they will not happen because the UN says that they have to. They will happen if the world body — all of us — come together. People from countries all over the world have to come out to fight.”

He said the bedrock for all of the goals to succeed, especially in Africa, was to stop the spread of AIDS, “the pandemic that is killing the culture and the fabric of our society.”

Youth speakers from Jamaica and Cambodia also underscored the devastating effects of the HIV/AIDS pandemic on their societies.

In a plenary discussion, a group of students from El Puente, a peace and justice group for teens in Brooklyn, addressed an issue that has become a major problem for American youth, especially in poorer, racially oppressed neighborhoods. The group, criticizing the government for allowing military recruiters free access to public schools, held up a collage showing photographs and news clippings of soldiers who were born in New York and slain in Iraq.

“How can we learn,” asked a young woman from the group, “when we are constantly being pestered by people trying to recruit us into the military?”

The day’s activities included the opening of a new photography exhibition showcasing the work of young photographers. The exhibit chronicles the lives of eight young people, linking their stories to the Millennium Development Goals, and depicts conditions in the Ukraine, Brazil, Morocco, Jamaica, Uganda, India and Cambodia. The photos tell stories of a young woman resisting sexual slavery, another young woman fighting for the right to education, a girl dealing with pregnancy in poverty and a young man coping with HIV/AIDS, among other themes.

“To all the boys and girls who have taken these stunning pictures and shared their dreams and fears,” said Thoraya Obaid, executive director of the United Nations Population Fund, which sponsored the day with other organizations, “let’s send a message: The cameras you used were disposable, but your dreams for a better future live on and are shared by many.”

The exhibition runs until Oct. 30 at the United Nations headquarters, and is open to anyone with a valid photo ID.