A diplomatic dispute between Spain and Italy over the surge of tens of thousands of migrants into the Spanish territory of Ceuta intensified on Saturday, as Madrid announced border controls on Italian travelers in retaliation for Rome's decision to impose restrictions on visitors from Spain.

Ceuta is one of two Spanish autonomous cities on the North African coast — the only European Union territories on the African mainland — separated from Morocco by a fortified border fence. The enclave has long been a flashpoint for migration pressure, as it represents an external EU border on African soil.

According to Spain's state news agency EFE, Italians arriving at Barcelona airport faced random police checks after the new controls took effect overnight. The Spanish government stated the measures would remain in place for at least a month, following Italian Prime Minister Giorgia Meloni's rejection on Friday of Spain's warning that it would adopt "proportionate measures to protect the interests and dignity of its citizens" unless Rome lifted its own restrictions by an Aug. 9 deadline.

Italy began enforcing air and sea border controls on Spanish citizens on Aug. 1, after Meloni sharply criticized the progressive migration policies of Spanish Prime Minister Pedro Sánchez.

The conflict was triggered by the sudden arrival of 72,000 migrants from Morocco at Spain's North African enclave late last month. Although the majority of those migrants have since returned, more than 80 died — some drowning or being trampled in a stampede to cross a breakwater barrier, according to Spanish and Moroccan authorities.

The migrant surge into Ceuta also reignited the immigration debate within the European Union, where several leaders criticized Sánchez for policies they argued contributed to the massive influx. Hawkish EU figures such as Meloni pointed specifically to a Spanish government program offering amnesty to immigrants without residency permits who could demonstrate they had been living in the country for at least five months and had arrived before Jan. 1 of this year. Over 1 million people applied before the registration window closed at the end of last month.

The dispute comes against the backdrop of the EU's broader struggle to reconcile national sovereignty over borders with the bloc's commitment to free movement. The 27-member EU bloc operates a visa-free travel zone known as Schengen, enabling citizens of most member states to cross internal borders freely for work and leisure. Under EU rules, member states may temporarily reintroduce controls at internal borders in the event of a serious threat, such as one to internal security. However, the rules also stipulate that such controls should be used only as a last resort in exceptional circumstances and must be time-limited.

Meloni's office said Friday that Italian authorities "have no intention" of lifting border checks on people arriving from Spain by sea or air until at least Aug. 15 — six days past the Spanish deadline.

"Italy does not accept ultimatums or impositions from abroad about national security and border control," a statement from the Italian government read.

In the event of a repeat of migrant arrivals in Ceuta, Italy said it would reconsider the border checks "only when we are certain that there will be no security or terrorist risks for Italy, that there will be no new wave, and that there are no irregular migrants heading towards European territory," the statement added.