MADRID (AP) — A group of around 300 migrants stormed fences separating Spain’s North African enclave of Ceuta from Morocco on Wednesday, and 116 of them made it onto European soil, authorities said.

Seven policemen were burned by acid and quicklime, a skin irritant, allegedly thrown by some of the migrants as they overran border defenses, the Guardia Civil said.

Five of the immigrants who got into Ceuta required hospital treatment for their injuries, a Guardia Civil statement said.

The migrants launched their assault at around 9 a.m., just as many Moroccan police were at an open-air prayer ceremony marking the start of annual festivities.

The assault came a month after just over 600 migrants got past the high, barbed-wire fences in the year’s biggest assault.

Sub-Saharan Africans living illegally in Morocco try to enter Europe each year by scaling fences surrounding Ceuta and Melilla, Spain’s other North African enclave.

The two enclaves recently received reinforcements of 60 police officers each, the Guardia Civil said.

Those who make it across head for temporary migrant accommodation centers and are eventually repatriated or released.