BRUSSELS — EU Migration Commissioner Magnus Brunner warned on Thursday the bloc is vulnerable to unauthorized migration if control of its external borders depends on the goodwill of neighboring countries.

Brunner’s remarks came at an extraordinary meeting of the European Parliament’s civil liberties committee, a week after a major migration surge from Morocco into the Spanish exclave of Ceuta, which has reignited debate over how the EU should secure its frontiers.

“What we have seen in Ceuta during the past few days was … a test of our resilience and also of the security of our external borders,” Brunner said.