What is behind the surge in migrants reaching Spain’s Ceuta enclave?

Spanish army and Guardia Civil officers take positions next to the border of Morocco and Spain, at the Spanish enclave of Ceuta (Javier Fergo/AP)

About 8,000 people have streamed into the Spanish city of Ceuta from Morocco in the past two days in an unprecedented influx, most of them swimming around breakwaters and across the border to reach the Spanish enclave in North Africa.

The surge has strained relations between Morocco and Spain, with Spanish Prime Minister Pedro Sanchez cancelling a trip to Paris to make an unscheduled visit to Ceuta, where Spain has deployed military reinforcements and police along the border.