Smugglers forced more than 120 migrants from Ethiopia and Somalia - majority teenagers - off of a boat near the coast of Yemen on Wednesday, the International Organization for Migration announced in a statement.
The IOM found the shallow graves of 29 migrants on a beach in the southern province of Shabwa during a routine patrol and 22 migrants are reportedly still missing.
The statement says the smuggler forced more than 120 migrants into the sea Wednesday morning as they approached Yemen's coast.
The dead had been buried quickly by the survivors and the International Committee of the Red Cross were working with the IOM to appropriately care for the remains of the deceased, the IOM said. They also told the migration agency that the smuggler went back to Somalia to pick up more migrants.
IOM spokeswoman Olivia Headon said: "They were all quite young, the average age was around 16".
De Boeck called the suffering of migrants on the route enormous, especially during the current windy season on the Indian Ocean.More news: USA claims to speak with one voice on N. Korea
"Too many young people pay smugglers with the false hope of a better future", he said. More than 30 000 of them are minor and originate from Somalia and Ethiopia.
The migrants, travelling to Yemen in search of new opportunities in the Gulf, had travelled a route taken by 55,000 others from their region this year.
Despite conflict and a dire humanitarian situation, Yemen is still seen by many Africans as a gateway to the rich Gulf states or Europe, and thousands make their way there every year in crowded boats.
Some Somalis are desperate to avoid years of chaos at home with attacks by homegrown extremist group al-Shabab and deadly drought. It is estimated that a third of those who undertake this perilous route are women.
According to the IOM, the 29 teenage migrants are among the more than 100 who were pushed into the sea.