Humanitarian NGO Sea-Eye, which runs the rescue boat Prof Albrecht Penck, said that while the asylum seekers it had on board its vessel a few days ago were allowed to disembark in Malta, a crew exchange for the vessel itself was denied.

On Wednesday, the 49 migrants who ere on board two NGO vessels outside Malta were transferred onto AFM vessels and brought to Malta to be redistributed to eight European Union countries.

Addressing a press conference at Castille, Muscat had said on Wednesday that the eight countries that will participate in the exercise are Germany, France, Portugal, Ireland, Romania, Luxembourg, the Netherlands and Italy.

The two NGO vessels however, were then told to leave Maltese territorial waters.

The Sea-Eye NGO said that the use of state power to take such measures to prevent aid agencies from saving human lives reveals Malta's political course.

"Premier Joseph Muscat has kept the crews of Professor Albrecht Penck and Sea-Watch 3 for weeks as political hostages to put pressure on the other EU member states," the NGO said, highlighting that the vessels were kept out at sea, not allowed to dock in Malta for weeks.