Although hundreds of migrants have tried to cross the fence before now, "we haven't seen a number like 700 before," Madrid says.
An unprecedented group of 700 migrants have tried to cross the fence into Spain's Melilla enclave overnight but were rebuffed by Moroccan border forces, a Spanish official said.
"There were about 700 people who tried to reach the border fence," a spokesman for the Spanish government delegation in Melilla told AFP on Friday.
None of the group, all of whom were from sub-Saharan Africa, were able to cross thanks to coordination between the Spanish and Moroccan security forces, the spokesman said.
Although hundreds of people had tried to cross the fence before now, "we haven't seen a number like 700 before", he said, describing their efforts to reach the fence as "very well-coordinated".
"It was very well organised, they were trying to reach different points of the border fence at the same time, to split up the security forces who were trying to stop them," he said, describing the approach as "relatively new".
"There are those who lead, those who split off and those who act as scouts, in other words everything is perfectly coordinated and planned."
Magnet for migrants
Spain's two tiny enclaves of Ceuta and Melilla have Europe's only land border with Africa, making them a magnet for migrants desperate to escape grinding poverty and hunger.
Several groups of hundreds of migrants tried to scale the Melilla fence throughout August, although most were rebuffed. In late July, more than 230 people managed to cross in one of the largest successful influxes in recent years.
In mid-May, Spain was caught off guard when more than 10,000 people swam or used small inflatable boats to cross into Ceuta as the Moroccan border forces looked the other way.
The influx came during a diplomatic crisis between Spain and Morocco, with Madrid angering Rabat by allowing the Western Sahara separatist leader to be treated at a Spanish hospital.
The border breach was widely seen as a punitive move by Morocco.