The vessel was detained in the port of Palermo for 11 hours for an inspection the NGO Seawatch International called "arbitrary."
The German humanitarian group Sea-Watch condemned on Sunday the blockade of its ship in the Sicilian port of Palermo by Italian authorities as "politically-motivated" after an 11-hour inspection.
Philipp Hahn, head of the Sea-Watch 4 mission, called the justification "flimsy" and a "systematic move to prevent civil sea rescue operations in the central Mediterranean."
The main reason cited was that saving lives did not conform to the vessel’s registration. Italian officials also said there were too many life jackets on board while at the same time that the boat's sewage system was not adequate for the number of people rescued.
It is the fifth rescue ship blocked by Italian authorities in as many months. The Sea-Watch 4 is operated by four humanitarian groups, including Sea-Watch and Doctors Without Borders.
The vessel had rescued 354 people, including 98 unaccompanied minors, families, pregnant women and children. It waited for days to be assigned a safe port, until survivors were transferred to a ferry for quarantine. The Sea-Watch 4 crew also underwent a two-week quarantine off Palermo.
"The Sea-Watch 4 is only at sea because of the absence of state-led search and rescue capacity at the world’s deadliest sea border," Doctors Without Borders said.
It accused Europe of "disregarding its legal and moral duty to save lives," also citing policies to reinforce the Libyan Coast Guard to block smugglers’ ships from leaving the country, which is not considered a safe haven and where many have reported torture.
So far this year, 379 people trying to reach Europe via Libya have died or gone missing on the perilous Mediterranean Sea crossing, 111 of those in August, the group said.
Meanwhile, the German-flagged ship Alan Kurdi, operated by Sea-Eye, rescued 114 people Saturday in two operations. The Alan Kurdi was the first to be detained in early May after disembarking 150 people.