Key questions answered as a rescue boat with 629 refugees and migrants heads to Spain after being denied entry in Italy.

There is growing concern for the lives of hundreds of refugees and migrants after a search and rescue ship drifting afloat the Mediterranean, with more than 600 onboard, was denied the right to dock in Italy and Malta – the two closest countries.

The Aquarius, which is jointly operated by SOS Mediterranee and Doctors Beyond Borders (known by its French acronym MSF), rescued 629 people from the Mediterranean Sea and remained unable to dock since Saturday.

The ship is now headed to Spain, which offered to give it safe harbour in the eastern port of Valencia, despite concerns raised by MSF officials, saying disembarking at the closest port was preferable to a journey of an extra four days.

Here are five key things you should know.

Who is on board?

More than 500 of the 629 migrants and refugees have now been transferred to two Italian coastguard and navy vessels, who are accompanying the Aquarius to Spain.

After the transfer, 51 women, 45 men and 10 children are left onboard the Aquarius, MSF said on Twitter on Wednesday.

Of the 629 people, there are 11 children, seven pregnant women and 123 unaccompanied minors, according to MSF.

The refugees and migrants are mainly sub-Saharan Africans who had set off from the coast of Libya to reach Europe.

The charity said the group were picked up in six different rescue operations off the coast of Libya and included hundreds who were plucked from the sea by Italian naval units and then transferred to the Aquarius.

Where is the ship now?

The Aquarius is south of Sicily and is expected to enter the Sicilian channel on Wednesday evening, MSF said on Twitter.

UPDATE: People onboard #Aquarius tell #MSF team they are glad to be finally heading to a port of safety after being rescued in #Mediterranean but above all not to be returning to #Libya. pic.twitter.com/isj5LvLDys — MSF Sea (@MSF_Sea) June 12, 2018

How are the conditions?

Before the transfer to Italian navy vessels, Aloys Vimard, a project coordinator for MSF, said the boat was “overcrowded and above capacity”

After days of drifting the Mediterranean, “people are weak, tired, exhausted,” Vimard told Euronews.

MSF has also expressed concern over the condition of patients who had to be resuscitated after rescue, saying they could develop “significant pulmonary issues after swallowing sea water.”

The Italian coastguard has resupplied the refugees with oranges, cereal bars and bread.

“It’s a welcome delivery but the MSF medical team are still concerned about nutritional needs being met over the three-day journey,” the charity group said.

Weather conditions are expected to “worsen on Wednesday night with waves up to 4 metres and winds up to 35 knots (65 kilometres per hour),” MSF said.

Why was entry denied?

Italy’s new populist government refused to give the Aquarius docking rights on Monday, citing “illegal immigration”.

“From now also Italy begins to say NO to the traffic of human beings, NO to the business of illegal immigration,” Matteo Salvini, Italian interior minister and head of the far-right League party, wrote on Twitter on Sunday.

{articleGUID}

“My goal is to guarantee a peaceful life for these children in Africa and for our children in Italy,” added Salvini, who is also a deputy prime minister after campaigning on a staunchly anti-immigrant platform, vowing to “put Italians first” and send hundreds of thousands of undocumented migrants “home”.

Italy had asked that those on board are made to disembark in Malta, a fellow European Union (EU) member state.

Malta, however, said it had nothing to do with the rescue operation.

“Malta is neither the competent nor the coordinating authority in this case. Malta will observe prevailing laws,” its government said in a brief statement.

When will it reach Spain?

The MSF estimates the Aquarius will reach Valencia on Saturday evening, depending on the weather conditions.