A Spanish aid organisation says it has recovered five bodies from waters off the Libyan coast and fears that at least 240 migrants could have died after two boats capsized in the Mediterranean.

Proactiva Open Arms spokeswoman Laura Lanuza said each rubber boat usually holds 120 people but smugglers tend to fill them over capacity to maximise their benefits on each trip.

She said the non-governmental organisation (NGO) confirmed the sinking of two boats but was only able to find the bodies of five men of African origin on Thursday morning, about 21 kilometres) north of the Libyan town of Sabratha.

The migrants were between 16 and 25 years old and appeared to have drowned, said Ms Lanuza, as their bodies did not show any sign of violence.

The NGO's rescuers were searching for a third boat.

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