Six migrants have drowned off northern Morocco trying to reach Spain, authorities said on Saturday, the latest deaths in a surge of attempted sea crossings since June.

A total of 54 migrants swam out to an inflatable dinghy off El Kallat beach near Nador on Friday but the boat hit the rocks in heavy seas and six of the passengers died, local authorities said.

The other 48 would-be migrants made it back to shore where they received first aid, the authorities added.

The Nador branch of the Moroccan Association of Human Rights said the six dead were all Moroccan.

It said a second group of 40 male migrants successfully reached the Spanish coast on Saturday.

High-speed inflatables long used to transport narcotics from Morocco to Europe have increasingly been used to ferry migrants to Spain as well. Migrants have also used canoes, kayaks and even jet skis in their bid to find a better life inside the European Union.

In the week from July 10 to 17, the Moroccan navy said it rescued nearly 900 migrants, most of them from sub-Saharan Africa.