Migrants aboard the rescue ship Open Arms began jumping off the stranded vessel on Tuesday afternoon.
Around 11.19 am CEST, the NGO tweeted saying nine people had thrown themselves into the water “trying to reach the coast of Lampedusa”.
“Italian lifeguards and coastguards are trying to rescue them. The situation is out of control,” it wrote.
The ship, which rescued the migrants off the coast of Libya, has been stranded off the coast of Lampedusa for weeks, with Italy refusing to allow it to dock. That is despite six EU countries reportedly ready to take them in.
A Syrian man was the first overboard and was rescued by Italian authorities, who are caring for him, an Open Arms spokeswoman said.
Reuters reporters said Italian coastguards came to the rescue of those who jumped after.
Overnight, eight migrants on board the rescue ship requiring urgent medical attention were evacuated from the Spanish vessel to the Italian port of Lampedusa.
One other migrant accompanying them also disembarked.
Open Arms has said the situation on board is desperate and passengers are sleeping jammed together on deck and sharing two toilets.
There have also been reports that scuffles have been breaking out on board.
However, Italian Interior Minister Matteo Salvini accused the charity of exaggerating conditions on board, accusing the migrants who were taken ashore overnight of lying about their ages and illnesses.
What next for the migrants onboard?
Italy has taken a hard line on migrant entry, of the opinion it has borne too much responsibility for coping with African migration to Europe.
Open Arms said Monday that it understood the Spanish government would allow them to dock and get off the boat in Mallorca — the nearest Spanish port to where they are located.
