Italian authorities seized a charity's ship on suspicion it had helped illegal immigration by picking up migrants in the Mediterranean instead of letting Libya's coast guard take them back to North Africa, the aid group said.

The Spanish charity Proactiva Open Arms picked up 218 migrants who were in unsafe rubber boats in international waters off Libya's coast on Thursday, then took them to Sicily, the Italian coast guard said.

The charity ignored a message from the Libyan coast guard claiming responsibility for taking in migrants in that stretch of sea, the Italian coast guard added in a statement