The Ocean Viking charity ship rescued more than 40 migrants off the coast of Libya on Saturday, according to Doctors without Borders (MSF), which operates the vessel along with the French charity SOS Mediterranee.
The migrants, mainly Sudanese men and adolescents, were picked up during the second operation in 24 hours by the Ocean Viking, which rescued 85 people including four children on Friday.
Also in the Mediterranean, a Spanish humanitarian ship that has been stuck at sea for over a week because of Italy's refusal to let it disembark 121 migrants said it rescued 39 more people on Saturday, further complicating conditions on board.
The Open Arms boat said it made its latest rescue in international waters in the central Mediterranean, where it has been stranded for nine days after Italy and Malta denied it entry.
Open Arms founder Oscar Camps said that Malta offered to allow the 39 new passengers to disembark, but still rejected taking the 121 the boat rescued last week.
"We cannot evacuate 39 people and tell the rest that they have to stay," Camps said.
Malta said that it was willing to accept the 39 migrants since it had launched its own rescue operation to reach the boat that was in its designated search-and-rescue area before the Open Arms got there first.
But the Maltese government said in a statement that the other 121 migrants were picked up "in an area where Malta is neither responsible nor the competent coordinating authority. Malta can only shoulder its own responsibility since other solutions are not forthcoming."
Rescue ships face fines of 1 million euros if they enter Italian waters without permission, the latest move by Interior Minister Matteo Salvini to suppress the NGOs that he has compared to migrant taxi services.
Actor Richard Gere, who rented a boat to take food and water to the Open Arms on Friday, made a call for politics to be set aside when lives are in danger.