United Nations ? More than 250,000 children are fighting in wars around the world, while tens of thousands of girls are sexually exploited by combatants, a senior U.N. official said.

Many young fighters are recycled from conflict to conflict, Undersecretary-General Radhika Coomaraswamy told the U.N. Security Council on Monday.

She cited the case of a Sierra Leone boy named Abou, who was abducted from school by rebels at age 11. By the time he was demobilized at 15, he was a rebel commander.

His community accepted him back, but he was feared and isolated. Six months later, he joined rebels in Liberia and later Ivory Coast. Disarmed again at 18, Abou told U.N. workers he only knew how to fight.

Coomaraswamy, however, singled out Sierra Leone and Liberia as countries where the situation for children has improved. Civil wars in both West African countries ended in recent years.

She spoke at a Security Council meeting to examine the impact of a resolution adopted last year to stop the exploitation of youngsters in war zones by governments and insurgent groups.