Two migrants were injured after gunshots were fired at the overcrowded Moria migrant camp on the Greek island of Lesvos, on Wednesday evening.
The two migrants were transferred to the island's hospital as a precaution, while the unknown assailant or assailants are still on the run.
Police have launched an investigation into the incident.
Greece has been the first point of entry into the European Union for hundreds of thousands of people fleeing war or poverty at home, with most arriving on eastern Aegean islands from nearby Turkey.
Moria camp currently houses 19,000 people, almost seven times its capacity of 2,800 places.
No further details on the shooting or the conditions of the migrants have been released.