German aid group Sea Watch said Tuesday it has filed a case at the European Human Rights Court against Italy for refusing to allow its ship carrying 47 rescued migrants to dock.
The German NGO's spokesman Ruben Neugebauer said the group had taken the drastic step on Friday because of Rome's hardline attitude against the mainly sub-Saharan migrants that its ship Sea Watch 3 pulled out of the Mediterranean on January 19.
Italy's Interior Minster Matteo Salvini is "taking the people on board as political hostages", said Neugebauer.
"They are trying to push it to the Netherlands," he added, referring to Salvini's insistence that the Netherlands or Germany take responsibility for the migrants.
Sea Watch 3 is sailing under the Dutch flag and currently sheltering from bad weather off Sicily.
Neugebauer stressed that laws governing international waters are clear that ships in distress "must be brought to the nearest safe harbour".
Migrants rescued by ships have frequently been left in limbo since Italy's anti-immigration government began turning them away last summer.
In a similar case earlier this month, the EU struck a deal to share out between eight European countries nearly 50 migrants stranded aboard two ships, one of which was Sea Watch 3.
Salvini, who has warned that he was considering legal action against Sea Watch's crew, said Tuesday that the 47 migrants can disembark if they agree to leave for Germany or the Netherlands.
"Disembarking of migrants? Only if they head for the Netherlands, whose flag the Sea Watch boat is flying, or to Germany, the country of the NGO," he said on Twitter.
"In Italy we have already received, and spent, too much."
Read: Italy says stranded migrants can land if they head elsewhere
The Netherlands on Monday rebuffed Italy's call to take in the 47 migrants, arguing that Dutch-flagged ship had acted "on its own initiative".
"It was up to the captain of Sea Watch 3 to find a nearby port to disembark the 47 migrants he had on board," said the Dutch government.
Some 113,482 migrants crossed the Mediterranean to reach Europe last year, according to the UN refugee agency, which said 2,262 people lost their lives or went missing making the perilous journey.
Europe has been wrestling with the problem since the migration crisis of 2015 when more than one million people arrived on its shores, many of them fleeing conflict in the Middle East.