When Fatima Zahra heard the rumour of a rare border opening between Morocco and Spain, she joined thousands in rushing to attempt a perilous journey into the Ceuta enclave by land or sea.

Hundreds of migrants are swimming from Morocco to the tiny Spanish territory of Ceuta at the country’s northern tip, overwhelming border security, local authorities said Wednesday.

Hundreds of migrants have entered the Spanish north African exclave of Ceuta by sea in recent days, officials said Thursday, with local television images showing them swimming…