The new Italian interior minister reportedly refused to allow it to dock
A rescue ship with over 600 people on board has been left in political limbo after Italy refused to let the vessel dock.
The Aquarius has 629 people on board - including 123 unaccompanied minors, 11 children and seven pregnant women - from six different operations in the central Mediterranean.
The new Italian interior minister, Matteo Salvini, reportedly refused to allow it to dock at Italian ports.
Mr Salvini, whose far-right League Party's tough line on immigration won it a record number of votes in March's election, has promised to deport half a million illegal migrants from Italy.
He was sworn in as the country's interior minister on June 1st, after the formation of an awkward anti-establishment coalition.
The medical charity Médecins Sans Frontières (MSF) say the rescue of two rubber boats "turned critical" when one boat broke apart in the darkness, leaving over 40 people in the water.
After taking 229 people from these boats, the rescue ship then took 400 more people, rescued earlier by Italian navy, Italian coastguard and merchant vessels.
MSF say it is "concerned" that "again politics are being placed above people’s lives.
"The priority must be the importance of the well being and safety of the people on board."
MSF project coordinator Aloys Vimard says the rescue vessel has enough food and on board to keep the people for two to three days.
States and actors involved should rapidly find solutions to allow migrants and refugees on board the #Aquarius to disembark safely and quickly. Hundreds of people urgently need assistance, slowing down operations puts their well being at risk https://t.co/skNTHQN80f— UNHCR Italia (@UNHCRItalia) June 10, 2018
The United Nations Refugee Agency in Italy, UNHCR Italia, says: "States and actors involved should rapidly find solutions to allow migrants and refugees on board the Aquarius to disembark safely and quickly.
"Hundreds of people urgently need assistance, slowing down operations puts their well being at risk".
The vessel was told to ask Malta to provide a disembarkation port, but Malta has also refused.
The rescue charities insist their role is simply to save lives, and that returning people to Libya is not an option because of the dire security situation in the country.
However, critics claim the presence of rescue charities in the Mediterranean encourages more migrants to attempt the crossing.
Between January and May this year, more than 22,500 migrants had reached European shores: 42% arrived in Italy from Libya and the remainder were divided between Greece, from Turkey (38%) and Spain, from Morocco (20%), according to the International Organisation for Migration, the UN Migration Agency.
Conditions for migrants who are either held in smuggler-run camps in Libya or sent back there from failed attempts to reach Europe are grim.
Additional reporting: IRN