Almost 500 migrants have broken through gates and forced their way into Spanish territory in Morocco.
Around 700 migrants simultaneously tried to smash through several gates in the 20ft fence which separates Spain's Ceuta enclave from Morocco.
A Ceuta regional government official said 498 migrants made it into Spanish territory following the 6am incident, in which more than 50 people were injured.
According to the Civil Guard, a surveillance camera showed hundreds of people approaching the fence, using tools and clubs to break one of the gates.
In video filmed by local media, some migrants can be seen with blood on their faces and bruises, but mostly celebrating their arrival in Spanish territory. Some wrapped themselves with Spanish and European flags and shouted "Freedom!"
More than 30 migrants were treated at a migrant centre for bone fractures and other injuries, such as cuts sustained while trying the scale the fence which is topped with barbed wire. Two migrants had to be taken to hospital to be treated for their injuries.
The official added that 11 Spanish police were also hurt in what is thought to be the biggest border invasion in recent years.
A Civil Guard spokesman said police clashed with the migrants at the Tarajal area of the fence, and at least 10 members of Morocco's armed forces were also injured.
Hundreds of sub-Saharan African migrants fleeing poverty and violence live illegally in Morocco and regularly attempt to enter Ceuta and Melilla, Spain's other North African enclave, in the hope of getting into Europe.
On Friday, 55 of them were rejected, according to the Civil Guard, because those who are intercepted on the spot can be returned to Morocco.
Those who make it over the fences are usually taken to migrant centres and eventually repatriated or let go, many choosing to seek asylum or work informally in Spain or other European countries.
Before the latest arrival, the migrant centre at Ceuta was already struggling to cope with more than 600 people and using military tents in nearby car parks.