Two women and a child were left to die at sea by Libyans who had come to rescue them, a Spanish non-governmental organization (NGO) said on Tuesday.
The three migrants were found floating near a wrecked dinghy, and there was only one survivor, a woman, the Proactiva Open Arms charity said on Twitter.
"The Libyan coastguard said they intercepted a boat with 158 people aboard and gave them medical and humanitarian assistance," Proactiva Open Arms founder Oscar Camps said.
"What they did not say is that they left behind two women and a boy and sank their boat because they did not want to board on the Libyan patrols," he added.
Camps said Proactiva's team could "not do anything" to save the dead woman, while the boy next to her "apparently died a few hours" before the NGO intervened.
The Libyan coastguard was not immediately available for comment.
Proactiva Open Arms is one of the NGOs that Italy's new populist government has banned from taking rescued migrants to Italian ports. Earlier this month, the group was forced to take migrants to Barcelona.
NGOs complain these restrictions are seriously hindering their work, leaving migrants' fate in the hands of a poorly-equipped Libyan coastguard.
But Italian Interior Minister Matteo Salvini has been unrepentant, writing on social networks that the blockade against Proactiva Open Arms' vessels was still valid.
"They can save their time and money, they will only see Italian ports from a postcard," Salvini, who is also deputy premier, wrote on Facebook and Twitter.
