Spanish Prime Minister Pedro Sanchez has criticized what he described as a lack of European Union solidarity over the migrant crisis in Ceuta, accusing some member states of responding with prejudice and political attacks instead of support.

Axar.az reports, citing Euronews, that Sanchez made the remarks in a letter sent to European Commission President Ursula von der Leyen.

The letter, sent on Saturday and seen by Euronews, comes after Sanchez described the arrival of 50,000 migrants from Morocco in Ceuta in a single day, after the double-fenced border was breached, as an "attack" and a "violation of Spain's territorial integrity".

In the strongly worded letter, Sanchez describes the response from some EU partners as "rather asymmetric".

While breaches of national borders are often swiftly condemned by member states and often portrayed as hybrid attacks, several EU countries instead called for tighter controls on Spain, urging Madrid to restore order rather than expressing solidarity.

"Most have shown us their support and solidarity, and have offered their assistance," the Spanish premier writes in the letter.

"Others, however, have chosen to attack Spain and to call for its temporary exclusion from the Schengen Area," he continued, in an apparent reference to Italian Prime Minister Giorgia Meloni's government, which on Friday announced it would suspend freedom of movement with Spain, even as migrants were returning to Morocco.

It remains unclear what the measure would mean in practice.

It is should be noted that 69,500 migrants entered the Spanish enclave of Ceuta from Morocco over the past 30 hours.

The death toll from clashes between migrants and security forces has risen to 67.