Moroccan forces beat back crowds with batons and tear gas at the gates to Ceuta, trying to prevent more storming across into the tiny Spanish territory that juts on a spit of sandy land into the Mediterranean from Morocco.
Spain's interior ministry said about 50,000 people had crossed the border since Thursday morning, and estimated about 25,000 had already turned and gone back.
Juan Jesus Vivas, head of Ceuta's local government, said as many as 60,000 people had pushed across and 34 had died.
The mass storm of the border caused division in Europe, where leaders of fellow EU states called for Spain to ensure that the incident was contained.
Right-wing parties around the continent blamed the incident on Spain's comparatively lax migration policies, including an amnesty granted to hundreds of thousands of unauthorised migrants in 2026.
France said it was increasing checks on its border with Spain, and Italy threatened to suspend Spain from the EU's internal open-border scheme.
Reuters at the enclave's border saw Moroccan police in riot gear using tear gas to disperse some of the people amassed near the fences.
Water cannon trucks were deployed and the charred remains of a bus and seven cars could be seen from clashes with the crowds.
On the other side, Spanish military vehicles lined up along sections of the border as dozens of migrants watched from a hilltop in Morocco, unable to cross.
Several hundred people could be seen returning to Morocco through border posts and holes in the fence, with some saying they could not find food or shelter in Ceuta.
"Honestly, I don't even know why I came, and now I'm going back," a young Moroccan man, who said he was from Tangier, told Reuters.
"I haven't eaten since lunch yesterday, even though I brought some money with me ... What we're doing is neither good nor enjoyable."
Spanish Prime Minister Pedro Sanchez travelled to Ceuta on Friday, where he was greeted with insults from protesters.
He called the mass crossing "a violation of Spain's territorial sovereignty" and said authorities were speeding up the repatriation of those who had entered illegally, with full co-operation from Morocco.
Ceuta and Melilla, Spanish autonomous cities in northern Morocco, have the European Union's only land borders with Africa.
Both periodically experience surges in attempted crossings by migrants seeking to reach Europe, but the scale of Thursday's rush appeared unprecedented.
In a post on X, Spain's Guardia Civil police association AUGC said there had been too few police in place to monitor the fence during the surge on Thursday, making them unable to stop the rush.
Territorial Policy Minister Angel Victor Torres said that among factors contributing to the surge might have been a ruling by Spain's Supreme Court in July that migrants intercepted at sea while attempting to reach Ceuta or Melilla cannot be summarily returned under special rules.
Migration is one of the most divisive issues in Europe, where far-right parties have been on the rise and much of the political mainstream has backed tougher policies.
Spain's Socialist government, an outlier to the continental trend of tightening rules, says it remains firm over illegal crossings but that immigrants benefit Spain and help strengthen its fast-growing economy.
It offered a mass amnesty that saw hundreds of thousands of people seek legal residency in the past months.
French Interior Minister Laurent Nunez said he had already issued instructions "to immediately step up checks at the Spanish border".
Italy's right-wing Prime Minister Giorgia Meloni said her country was prepared "to intervene with extraordinary measures to defend the borders and the safety of citizens, including the suspension of the Schengen Area with Spain".
