MADRID, May 9 (Reuters) - Around 300 sub-Saharan African migrants stormed the six-metre razor-wire fence between Morocco and the Spanish enclave of Melilla early on Tuesday, with around 100 successfully crossing the border, police said.

Three police officers were injured and required medical attention after the 0500 GMT rush, after migrants threw stones at border security, Spanish police added.

Spain's two enclaves in Morocco, Ceuta and Melilla, are often used as entry points into Europe by African migrants, who either climb over border fences or try to swim along the coast.

Over 1,000 migrants attempted to cross into Ceuta in January, but most were returned to Morocco.

(Reporting by Raquel Castillo, Writing by Paul Day, Editing by Sarah White) ((paul.e.day@thomsonreuters.com; +34 91 585 83 08; Reuters Messaging: paul.e.day.thomsonreuters.com@reuters.net))