A resurgence of violence in Congo reached a pinnacle this week as M23 rebel fighters seized Goma and a nearby international airport, increasing widespread concerns amongst humanitarian organizations that some of those fighting on the front lines are child soldiers.

The rebel force — originating from soldiers who defected from a Congolese militia seven months ago — has stretched its influence across the North Kivu province bordering Rwanda, on Tuesday capturing the provincial capital, which is home to one million people.

The U.S.-based Human Rights Watch has accused the M23 of using child soldiers, defined by the UN as anyone conscripted under age 18.

International law identifies any person under that age who is being involuntarily used by an armed group, whether as a sex slave, cook, porter, spy or messenger, to be considered a child soldier.

An opportune time

Human Rights Watch says children are being recruited on both sides of the Congo-Rwanda border, as part of the ongoing battle that the M23 indicated Wednesday would not end until the rebels capture Congo's capital.

Shelly Whitman, director of the Halifax-based Child Soldiers Initiative, housed at Dalhousie University's Centre for Foreign Policy Studies, on Wednesday was in Musanze, Rwanda, one hour northeast of Goma.

"Even though we're not very far away, people are very calm," she said

Whitman is taking part in a UN course aimed at training national level troops and peacekeepers in the region on how to approach child soldiers.

"It’s an extremely opportune time because of what’s happening," Whitman said. “There's been a heavy use of children in Congo and it’s not a secret to anybody.

"Every incarnation of every group there has used them at one point or another.”

That includes the Congolese government, which according to local media reports handed out weapons to children as M23 rebels rolled into Goma, Whitman said.

M23 rebel leader Sultani Makenga, left, sits in a truck in Goma, Congo, on Wednesday, soon after the rebels captured the city from the government army. Makenga has been sanctioned by the UN and U.S. for using child soldiers. (James Akena/Reuters)

In a report to be released Friday, the United Nations accuses the M23 of grave crimes including recruiting child soldiers, summary executions and rape, according to research by the UN Group of Experts.

The international community has been slow to act on the issue, but both the UN and the U.S. agreed to sanction M23 Col. Sultani Makenga recently for allegedly having abetted the conscription of child soldiers.

Bosco Ntaganda, another prominent figure within the rebels ranks, was indicted by the International Criminal Court in 2006 on three counts of crimes against humanity, as well as seven for the conscription and enlistment of child soldiers.

Witnesses have told Human Rights Watch that most of the children used in the Congo conflict were abducted from their homes,from markets, or while walking to their farms.

"There are lots of children with Ntaganda now and they send us to the front lines so we're the first to die. It's as if they take us to kill us," a former child soldier told the organization.

Whitman estimates there are about 200,000 children in Congo's conflict region that could potentially be exposed to the flow of small arms.

2 leaders meet in Uganda

Rwanda has been accused by the Congolese government as recently as this week for propping up the rebel fighters with weapons.

Rwandan President Paul Kagame and Congolese President Joseph Kabila met Wednesday in the Ugandan capital of Kampala, in a meeting mediated by Ugandan President Yoweri Museveni.

With the UN estimating there are 250,000 child soldiers fighting around the world, Whitman said that protecting children should be a condition of any talks "to protect the most vulnerable."

“If there are any negotiations going on, this should be the top issue right now."

With files from The Associated Press