A sudden influx of migrants swimming into the Spanish enclave of Ceuta in northern Africa is a serious crisis for Europe, Prime Minister Pedro Sanchez said on Tuesday, although Spain and Morocco both gave signs of seeking to defuse a tense situation.

Spain deployed troops to Ceuta to patrol the border with Morocco after as many as 6,000 migrants, including some 1,500 minors, entered the enclave on Monday and Tuesday by swimming in or climbing over the fence. Soldiers in armoured vehicles were guarding Ceuta's beach on Tuesday.

A Reuters reporter on the ground said the number of arrivals by sea had slowed, and a number of those who had arrived were voluntarily returning to Morocco. Spain said approximately 2,700 migrants had already been sent back to Morocco, where they were being accepted under a readmission deal.

The regional leader of Ceuta criticised what he described as Morocco's passivity in the face of Monday's surge, and some independent experts said Rabat had initially allowed it as a means of pressuring Madrid over its decision to admit a rebel leader from the Western Sahara to a Spanish hospital.

However, the Spanish government did not make that connection but rather maintained a positive tone towards Morocco, with Sanchez calling the north African nation a friend of Spain and the interior ministry citing cooperation over the readmissions.

Moroccan TV footage showed the authorities setting up barriers on Tuesday to prevent people from crossing into Ceuta.

"This sudden arival of irregular migrants is a serious crisis for Spain and Europe," Sanchez said in a televised address to the nation before he was due to travel to Ceuta.

"I want to tell all Spaniards, especially those in Ceuta and Melilla, that we will re-establish order in your city and at our borders with the utmost speed. We will act firmly to ensure your safety," he said.

European Commission Vice-President Margaritis Schinas tweeted that the enclave's frontier was a European border, expressing his "full solidarity with Spain" and calling for a European pact on migration and "strong protection of our borders".

Ceuta, with a population of 80,000, is located on the northern tip of Morocco across from Gibraltar. Along with Melilla, it has long been a magnet for African migrants trying to reach Europe in search of a better life.

Morocco has a claim on Ceuta and another Spanish enclave, Melilla.



The spike in arrivals took place after Rabat expressed its anger last month when Spain discreetly admitted Brahim Ghali, the leader of Western Sahara's rebel Polisario Front to a Spanish hospital.

Morocco's Foreign Ministry had issued a strongly worded statement criticising what it said was Spain's decision to admit Ghali under a false identity without informing Morocco, warning of repercussions for relations between the countries.

Moroccan authorities did not respond to requests for comment on Tuesday.

"This is happening because of the absolute passivity of the Moroccan authorities," Ceuta regional leader Juan Jesus Vivas told 24H TV channel, referring to the sudden arrival of migrants.

He said the situation was chaotic and it was impossible to say how many migrants had entered.

Rafael Calduch, professor of international law at Madrid's Complutense University, drew a link between the Ceuta situation and the tension over Ghali.

"The passivity of Moroccan police is a direct consequence of the hospitalisation of Ghali in Spain," he said.

The Polisario Front wants the Western Sahara to be an independent state rather than part of Morocco. Algeria, Morocco's regional rival, backs the Polisario Front.

The United States in December recognised Moroccan sovereignty over the Western Sahara territory.

Spanish Foreign Minister Arancha Gonzalez Laya told Cadena SER radio on Monday evening that Ghali was accepted into Spain on humanitarian grounds.

(Reporting by Belen Carreno, Joan Faus, Cristina Galan and Inti Landauro, Writing by Andrei Khalip and Ingrid Melander, Editing by Estelle Shirbon) ((Inti.Landauro@thomsonreuters.com))