Hundreds of sub-Saharan Africans infiltrated Melilla, a Spanish-controlled area in Morocco on Wednesday, in what Spanish authorities described as the largest such operation to take place in the area.
Morocco is one of the main launching areas of illegal migration into Spain from North Africa. Melilla, a coastal enclave in northern Morocco, is controlled by Spain.
Many immigrants have in the past sought to enter the area, seeking a better life in Europe.
Spanish authorities said nearly 200 people managed to climb over the three-meter-high barbed wire fence using wooden ladders. An additional 100 people managed to cross the border a day earlier in a similar move, the Morocco Times reported.
Dozens of people, including security forces, were injured in stampedes.
Spain announced a few weeks ago it will raise the height of the Melilla border fence, which was built in the late 1990s, to stop the flow of illegal African immigrants.
Construction is due to be completed by the end of the year.
Meanwhile, Spanish authorities say more than 11,000 people have tried to penetrate the area since the beginning of 2005.
In most cases the would-be immigrants claim asylum to prevent immediate deportation but few applicants are successful.
Earlier this month the Moroccan Ministry of Interior said it had arrested more than 1,000 people trying to illegally enter Europe.