A human rights group is demanding an investigation into the fatal shooting of an ethnic Rohingya man who was among 21 to escape from an immigration detention center in southern Thailand.

The Rohingya migrant workers escaped from the center in Phang Nga province on Monday, and police shot the man in what they said was self-defense when he was cornered and assaulted them. Fourteen of the escapees were still at large Tuesday.

The Bangkok-based human rights group Fortify Rights said in a statement Tuesday that in addition to allowing an independent probe, Thailand should end the indefinite and arbitrary detention of refugees and human-trafficking survivors.

Rohingya, a stateless ethnic Muslim minority, face persecution and poor economic opportunities in Myanmar, their homeland. They're often exploited when seeking work abroad.