Madrid - More than 300 undocumented Africans on Tuesday stormed the fence surrounding the Spanish North African enclave of Melilla in an attempt to enter Spain.
Officials described the assault as "very violent," with migrants throwing objects at police officers trying to hold them back. Six police officers and one migrant were injured.
More than 100 of the migrants managed to enter Melilla, officials said.
About 80 migrants meanwhile swam into the Spanish enclave of Ceuta further west, police said.
Ceuta and Melilla, located on Morocco's northern coast, have long acted as gateways for undocumented migrants to enter Europe.
The six-metres-high fence surrounding Melilla has been reinforced with barbed wire, video cameras and sensors.
In 2006, three people were killed during a co-ordinated attempt by dozens of people to climb the border fence. Two of them were reportedly shot and fatally injured by Moroccan police, while one fell down from the wall.
Attempts to enter Melilla and Ceuta usually increase in the warm summer months.
Migrants also cross by boat from Morocco directly to the Spanish mainland.
The coast guard on Tuesday intercepted a boat carrying 17 Algerians.
Rescuers were meanwhile looking for 12 migrants who had gone missing after their rubber dinghy capsized in the Strait of Gibraltar on Monday. One body was retrieved from the sea, but police said it did not belong to any of the 12.
Spain's recession and record unemployment levels have not deterred African migrants.