LONDON—Children are traveling to Geneva from as far away as Brazil, South Africa, and the Philippines as part of a campaign to stop the abuses of child labor.

Four children, with adult chaperones, set out from Sao Paulo, Brazil, Feb. 25, taking part in the Global March Against Child Labor. To reach Washington, D.C., they will travel more than 4,600 miles, much of it on foot. They will then be flown to Geneva, where the International Labor Organization (ILO) begins a meeting June 1 to draft a new international convention on child labor.

Another group of children and chaperones set off from Manila, Philippines, in January, with more children due to leave from Cape Town, South Africa, March 21 and from London in May.

The organizers of the Global March Against Child Labor plan to hold a mass rally in Geneva to coincide with the ILO meeting.

There are 250 million child workers worldwide, many of them “modern-day slaves,” according to Christian Aid.

“Around the world from dawn to dusk you can find children working down mines, hunched over carpet looms, scrubbing their employer's floors,” says the charity. “Many are separated from their families and are working unpaid.”

In Asia child labor has been a prominent issue for the past 10 years, but in Latin America it is just recently coming under public scrutiny.

The Sao Paulo march will cross Brazil, Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala, Belize, and Mexico before reaching Washington en route for Europe.

The route of the Asian march is Philippines, Vietnam, Cambodia, Thailand, Malaysia, Bangladesh, Nepal, India, Pakistan, Iran, Turkey, and across Europe to Geneva.