For the second time this month, the authorities in Italy and Malta are refusing to allow a rescue ship with hundreds of migrants aboard to dock in their ports.

The rescue vessel, the MV Lifeline, run by the German charity Mission Lifeline, has been unable to offload 234 people sheltering onboard since they were rescued from two rubber dinghies in the Mediterranean on Thursday.

A cargo vessel, the Alexander Maersk, was also waiting on Sunday for clearance to dock in an Italian port with 110 rescued migrants onboard. While on a merchant mission on Thursday, the ship came to the assistance of a boat in distress 5 miles off the coast of Pozzallo, Italy.

"They have the right to live,” Axel Steier, a Mission Lifeline founder, said of the migrants. "And they have a right to seek asylum, and that isn’t being guaranteed at the moment. It’s kind of like you are jailed on the ocean.”

The episode is the latest to highlight divisions in the Europe Union that have left the bloc without a comprehensive migration policy as countries on the front line of the Mediterranean route bicker over who should be responsible for migrants.

Mr. Steier, who said the MV Lifeline was waiting off the western coast of Malta, described the rescue vessel as a "ball in a political game.” The migrants onboard, all of whom are from sub-Saharan Africa, had set off from Libya on two dinghies.

The group is mostly made up of men, with 14 women and at least four children among them, Mr. Steier said. He called the idea of transporting migrants back to Libya inhumane and contrary to international human rights norms.

Describing migrants’ accounts relayed to worked on the ship, he said, "We have women who have been raped, and also people who have been tortured.”