German charity Sea-Eye on Tuesday said it had come to the rescue of migrant boats five times in 24 hours, which showed "the state of emergency" in the Mediterranean.
Sea-Eye said it was alerted by the Alarm Phone migrant hotline, but did not say whether it had permission from Italian authorities to carry out the rescues, without which it risks having its ship seized.
"Five rescues in 24 hours. That shows the state of emergency in the Mediterranean at the moment, and how important it is that we are there to save lives," the charity said in a statement.
The Sea-Eye 4 responded to the distress calls along with two other rescue charity ships between Sunday and Monday, rescuing some 230 people, including a mother and her baby, it said.
After transferring some to an Italian coast guard vessel, on Tuesday it was transporting around 170 people to the assigned port in Genoa, in northern Italy, which it said was a six-day round trip.
Since coming to power in October 2022, far-right Prime Minister Giorgia Meloni's coalition has sought to stem the arrival of migrant boats into Italy from North Africa.
It accuses the rescue ships of being a "pull factor" -- although in reality the vast majority of migrants who arrive in Italy are picked up by the coastguard.
"By sending civilian rescue ships to distant ports... we are losing valuable time in the search and rescue zone, during which we cannot help people in need," said Sea-Eye chairman Gorden Isler.
"This policy can have fatal consequences for people seeking protection," he said.
Italian law requires that NGOs head "without delay" to a port immediately after a rescue is completed -- preventing them from carrying out several in a row.
The NGOs argue that it violates maritime law, which requires any ship to come to the aid of a boat in distress.
But failing to comply risks a fine of up to 10,000 euros ($10,725), and potentially the temporary or definitive seizure of the vessel.
Many charity ships have been detained -- sometimes repeatedly -- for breaking the law, although those detentions are sometimes overturned by the courts.