SAD! Smuggler Drowns 50 Migrants
The International Organisation for Migration statement calls the incident "shocking and inhumane".
It says staffers found the shallow graves of 29 of the migrants on a beach in Shabwa during a routine patrol.
The statement says the smuggler forced more than 120 migrants into the sea on Wednesday morning as they approached Yemen's coast.
The narrow waters between the Horn of Africa and Yemen have been a popular migration route despite Yemen's ongoing conflict.
The statement says staffers provided aid for 27 surviving migrants who remained on the beach, while other migrants left.
The agency says 22 migrants are missing.