A charity that operates a rescue ship currently carrying more than 100 migrants off the coast of Italy has said that it could not accept an offer from Spain to dock in Algeciras, citing an emergency situation on board.

Open Arms' spokeswoman said: "We do not accept Spain as a port to go because we are in a state of extreme humanitarian emergency. What they need is to be disembarked now.

"It is unthinkable to navigate for six days; that is what it would takes for us to arrive to Algeciras."

Earlier, the Spanish government offered to take in the charity vessel Open Arms with more than 100 migrants on board because of what it calls Italy's "inconceivable" refusal to allow it to dock.

Prime Minister Pedro Sanchez said he "ordered the port of Algeciras to be ready to receive the boat Open Arms," which is currently in limbo off the Italian island of Lampedusa, his office said in a statement.

It cited the "urgent situation" on the vessel and the "inconceivable decision by the Italian authorities... to close all its ports" to the migrants.

The migrants, most of whom are African, were picked up by the Open Arms boat off the coast of Libya.

Italy's far-right Interior Minister Matteo Salvini has ordered his officials not to let the migrants disembark, though he made a partial concession yesterday by allowing 27 minors to leave the boat.