Moroccan police have arrested at least 111 people as they tried to enter the Spanish North African enclave of Ceuta.

Moroccan police arrested at least 111 people on Monday as they tried to enter the Spanish North African enclave of Ceuta, amid heightened security measures on both sides of the border after social media posts calling for another mass migrant crossing, Reuters news agency reported.

The attempted crossing came two weeks after more than 72.000 migrants entered Ceuta, sparking tensions within the European Union and fueling anti-immigrant rhetoric from far-right parties around the world. At least 96 people died trying to reach European soil.

A source at the Moroccan Interior Ministry told Reuters that those detained included 109 migrants from sub-Saharan Africa and two Moroccan nationals, arrested in or around Fnidek, a Moroccan city opposite Ceuta.

According to the Spanish news agency EFE, Moroccan police used tear gas to disperse groups of migrants gathered on hills about three kilometers from the border. Reuters later saw hundreds of police, some in riot gear and others in plain clothes, returning from the hills outside Fnidek.

EFE and Spanish state broadcaster TVE said the Moroccan Interior Ministry had ordered their journalists to leave Fnidek immediately, without giving a reason.

In Ceuta, Spanish soldiers guarded supermarkets and police patrolled the enclave's main streets in large numbers. The city was calmer than in the days following the deadly border crossing attempt on July 30.

Madrid has since set up a maritime barrier and deployed more than 500 additional police officers from mainland Spain, bringing the total number in Ceuta to more than 1.600. The Interior Ministry said the reinforcements would remain as long as necessary.

"We will continue to deploy as many members as necessary to restore normalcy as soon as possible and prevent events like those of July 30 from recurring," Interior Minister Fernando Grande-Marlaska said on Thursday.

About 5.000 migrants remain in Ceuta, the minister said. Reuters saw hundreds of them sheltering from the scorching heat under makeshift bamboo shelters on the city's El Trampolin beach.

Grande-Marlaska said migrants who entered irregularly would not be allowed to remain in the enclave, travel to mainland Spain or obtain legal status, except in rare cases of extreme vulnerability. Those who do not have the right to stay will be returned to Morocco, he said.

Morocco tightens controls

Earlier this week, Rabat said it was monitoring "the spread of posts and messages of unknown origin on social media" calling for a mass border crossing on August 15, warning that organizers and participants would be prosecuted.

A Reuters witness saw a heightened security presence near the border, including police vehicles with wire mesh screens and checkpoints on the roads. Local media reported similar measures near Spain's other North African enclave, Melilla.

Authorities have prevented several groups from boarding trains and buses to northern Morocco in cities including Casablanca, Fes and Kenitra. However, witnesses told Reuters that some migrants from sub-Saharan Africa were bypassing security checkpoints by using mountain roads towards Fnidek.

One witness said that schools in Fnidek had been converted into accommodation for members of the security forces deployed near the border.

"My advice — don't cross"

Many of the young people who entered Ceuta on July 30 were fishing, swimming or washing themselves on Tarajal Beach on Friday.

Dris Sadik, a 22-year-old from Fes, who said he swam for five hours to reach Ceuta, urged others not to follow his example.

"The most important advice I would give to people trying to cross: Don't cross now, my brothers. You will only suffer," he told Reuters.

A similar warning was issued by 17-year-old Adil Džamil.

"Those who enter will not benefit at all. There will only be more and more of us, and they will not be able to find a solution for everyone," he said.

Jamil said that mass border crossings are "planned by the people themselves," who choose a date, gather in Fnidek, and cross the border together so that their numbers give them greater strength.

"If I had stayed with my parents, I would have slowly died. But if I risk my life, get there and build my future... it will be better," he said.