ISLAMABAD, Pakistan — More than 170 million children worldwide are malnourished and 120 million never attend school, the executive director of the UN children's agency said Sunday, citing the critical role volunteers play in improving the lives of youths everywhere.

UNICEF chief Carol Bellamy also underlined the challenges of improving primary health care for children around the world, as she opened an international conference in the Pakistani capital to encourage volunteerism at aid agencies and in government.

"Children under the age of five are still dying at a rate of nearly 10 million a year from preventable causes like diarrhea, measles and acute respiratory infections,'' she told delegates at the conference.

More than 170 million children globally remain malnourished, and over 120 million young people, many of them girls, "never see the inside of a school,'' said Bellamy, who arrived in the Pakistani capital Sunday for a three-day visit to discuss co-operation in health and education projects.

Literacy rates are low in Pakistan. UNICEF estimates that three out of every 10 children aged five to nine never go to school, and dropout rates are high. Of those children who enrol, only half reach fifth grade, according to UNICEF.

Also addressing the conference, Prime Minister Shaukat Aziz invited volunteers to help Pakistan's government to fight "social challenges.''

"We recognize that the government alone cannot fight against illiteracy, disease, hunger, poverty and many other challenges,'' he said.

"The spirit of volunteerism is at the heart of all of our efforts to build a better future and a better future for every child,'' Bellamy said.

Bellamy is scheduled to hold talks with Aziz on Monday, then she plans to travel to the eastern city of Lahore to meet with senior government officials on UNICEF-assisted projects in Punjab province.

UNICEF is assisting with projects in child education, health care and the protection of women's and children's rights in Pakistan, an impoverished country of about 150 million people.