Spain's maritime rescue service has said it saved 476 migrants who were attempting to cross the Mediterranean from Africa.

The migrants were pulled from 15 small boats on Friday and Saturday, but there were no reported casualties.

Separately, a Spanish non-profit body dedicated to helping migrants at sea rescued 105 other migrants in waters near Libya on Sunday.

The aid group Proactiva Open Arms found the migrants, from Bangladesh, Egypt, Libya, Nigeria and other countries, drifting at sea in a motorless boat.

The migrants said human smugglers sailing in a separate boat removed their boat's engine halfway through the dangerous Mediterranean crossing and left.

Favourable weather appears to have sparked the surge in sea crossings.

Each year, tens of thousands of migrants attempt to reach Spain and other southern European countries by crossing the Mediterranean in smugglers' boats. Most of the vessels are unfit for open water, and thousands of migrants drown each year.

The UN says 615 migrants have died crossing the Mediterranean so far this year. A total of 22,439 migrants have reached European shores, with 4,409 arriving in Spain, through the first four months of 2018.