Image copyright Getty Images Image caption A migrant was saved from the sea by a rescue team
Leaders from the Netherlands, Denmark and France have condemned the boat capsizing in the English Channel which left 16 people dead.
The bodies of 12 people washed up on the north-east coast of France in a “horrific” shipwreck, according to reports.
Several others were rescued, with search efforts continuing for any more survivors.
Dutch Prime Minister Mark Rutte said the incident “underscores the dangers” of illegal migration.
Danish Prime Minister Lars Lokke Rasmussen also said he was “shocked” at the news, while French President Emmanuel Macron said the death toll was “very high”.
The fishing boat, known as the Mavi Marmara, was transporting migrants when it set off from the Moroccan coast on Wednesday, French officials said.
The rescue operation was carried out by EU border agency Frontex, backed by French and German coastguards and emergency services.
Frontex is tasked with patrolling the borders of the EU’s external borders to prevent people from travelling to Europe illegally.
You can read more about the case here.
Analysis by BBC European affairs reporter Ben Brown
“This is not about the vulnerable people aboard the boat, but the fact that this is at all possible.
“Nobody – apart from, perhaps, the smugglers – disputes that there are too many people trying to get into Europe illegally, illegally.
“The problem is that not enough people and politics are prepared to work out a practical, workable response.
“Attempts to control the flow of people through the erection of fences, along with other forms of deterrents, are fraught with risk, and often lead to illegal or violent incidents.
“This time, European border agency Frontex has undoubtedly prevented a huge number of deaths.”
Image copyright AFP Image caption The 24 survivors were transferred to a ferry to Benidorm in Spain
International Migration Director Laxman Singh Rathore said: “I call on governments around the world to ensure that refugees and migrants have access to safe, legal and regular pathways to migration and freedom from persecution.”
The 23 survivors were brought to the town of Calais, on the French coast, after being rescued by a patrol boat, French Interior Minister Gerard Collomb said.
He said six people were found on the sea floor of English Channel about 1km (0.6 miles) from where the boat hit the rocks.
Their nationality has not been disclosed.
Shocking loss of life as people smugglers’ boat sinks in English Channel leaving 12 dead: https://t.co/uRB8wCnUe8 pic.twitter.com/7pNKYOT5IP — British Phones (@BritishPhones) January 12, 2018
Mr Collomb has warned the current system is overloaded, and that migrants are risking their lives to come to France.
“The problem is that some of them bring their families as well. Every year in this country we see minors, who are going across the water at the moment at the same time,” he said.
Police in Calais said its officers are also seeing large numbers of unaccompanied children “out in the open and vulnerable to exploitation”.
The MV Ocean Lady had been in distress on Wednesday morning near Bodmin Moor, Cornwall, but its passengers were unable to communicate.
An RNLI lifeboat from Fowey, Cornwall, was the first to arrive at the scene and was given the urgent task of taking the surviving people to Bodmin.
An RNLI spokesman said: “It’s horrific. It’s a real tragedy.”
Image copyright Rex Features Image caption The RNLI lifeboat from Fowey, Cornwall, was first to arrive at the scene
See what some of you have been saying about the sinking:
As very sad news of the #ChannelVessels tragedy, especially such a sad loss of life. #Heartbreaking Image: man on Sky News
For this story please contact @SkyNewsNews. pic.twitter.com/EW3n4qJaUX — Royal Navy (@RoyalNavy) January 12, 2018
Our thoughts are with the survivors and families of the victims. We hope the search mission is a success and that those still missing are found safe and well. https://t.co/f0sHDmzI9W pic.twitter.com/OgDOOG2qoY — UK Coastguard (@UKCoastguard) January 12, 2018
This article contains material from the BBC News website.