Several migrants jumped into the sea from a Spanish rescue boat in a bid to reach shore in Italy.
Crew members, however, jumped in and brought them back aboard.
"Nine people have thrown themselves into the water trying desperately to reach the coast of Lampedusa," the ship Open Arms tweeted. "The situation is out of control."
Open Arms, with almost 100 migrants onboard, has been left stranded just off the port of Lampedusa after Italy denied permission from entering its waters.
Earlier, Italy's hard-line interior minister, Matteo Salvini, banned private rescue ships, saying they have become "taxis" for people smugglers.
“If the worst happens, Europe and Salvini will be responsible,” the charity said in a tweet.

Russia tests nuclear-capable Poseidon super torpedo
Hurricane Melissa hits Cuba hours after devastating Jamaica
Trump says Gaza ceasefire holds, Israel has right to hit back if attacked
South Korea welcomes Trump with its highest award, a golden crown and ketchup
Ex-Philippines president Duterte appeals ICC jurisdiction ruling
Cyclone Montha lashes India's east coast; kills one
At least 9 killed, 5 missing in central Vietnam floods
Arab League warns of war escalation, Israeli occupation practices
