The Spanish NGO rescue boat Open Arms has been at sea for 12 days and is currently sitting idle in the Mediterranean Sea with 151 migrants on board, some 50 km off the coast of the Italian island of Lampedusa, Efe news reported.
Meanwhile, another 375 migrants onboard the Ocean Viking, which has undertaken four rescue operations, is currently navigating international waters off the Libyan coast, where many migrants begin their perilous journey across the Mediterranean.
The nearest EU countries, Italy and Malta, have prohibited NGO vessels from entering their waters.
In the case of Italy, the country's Interior Minister Matteo Salvini said he would not alter his stance on refusing entry to NGO boats, who he accuses of aiding illegal immigration.
"Working at the Ministry this morning to prevent over 500 migrants on board two ships, one French and one Spanish, from landing," Salvini, leader of the League Party, said in a tweet.
"For 350 of them, Libya offered a port of landing, while for the others (those visited by the millionaire Richard Gere), the indication that I gave is the prohibition of entry into our waters and the invitation to sail towards Spain," he said.
Gere visited Open Arms last week and delivered supplies.
The European Commission said it was in contact with EU member states to find a solution to the stand-off with Open Arms but there appeared to be no concrete progress.
Onboard Open Arms, 151 migrants, including men, women and infants rescued near Libya, await their fate.
"Abandonment.... 151 invisible people continue to resist on the deck of Open Arms but every day that passes is more difficult. The infamous silence of Europe. The lack of humanity and empathy makes them more guilty," Open Arms said in a tweet.
On Monday, Maltese authorities agreed to evacuate two women suffering health problems, as well as six of their family members, from the Spanish NGO-run vessel.
A day before that, one man was transferred to a hospital in Lampedusa, which was previously a common drop off spot for NGO migrant rescue boats.
Meanwhile, the Open Arms crew warned that sea conditions were expected to worsen. The NGO petitioned the Spanish embassy in Malta to grant asylum to 31 minors on board Open Arms.
However, Spain's acting Minister of Development, José Luis Ábalos, said on Tuesday that the Open Arms crew did not have the judicial power to file an asylum request.
Óscar Camps, the founder of the NGO, dismissed suggestions the boat could navigate towards Spain, saying the five-day voyage could be dangerous for those on board. He called on Spain's acting Prime Minister Pedro Sánchez to defend Spanish organizations.
( With inputs from IANS )