Turkey migrant boat sinks in Bosphorus, killing 24
At least 24 people have been killed and scores are missing after a boat said to be carrying migrants sank off the north coast of Turkey, officials say.
The accident took place where the Bosphorus meets the Black Sea.
A large air, sea and underwater rescue operation has been taking place with many bodies being pulled from the water.
The nationality of the migrants is unclear but it is unusual for a vessel carrying migrants to be in this area.
One theory is that the refugees were trying to get to Romania or Bulgaria - both member states of the European Union.
Turkey is one of the main departure points for migrants aiming for the EU, but most travel across the Aegean to Greece, the BBC's Turkey correspondent Mark Lowen says.
The boats are often makeshift dinghies, usually overcrowded, with the migrants paying thousands of dollars to smugglers in Turkey.
Two months ago another group of migrants - mostly Syrians and Afghans - was rescued by the Turkish coastguard off the northern coast reportedly heading for the EU.
"The wind is making our task very difficult. The boat is a very small one. But they were carrying 40 people in it. We are seeing bodies of children floating in the sea," rescuer Ali Saruhan told Hurriyet Daily News.
Seven coastguard vessels and a helicopter were conducting the search in the Black Sea, some 5km (3 miles) north of the Bosphorus, the coastguard said in a statement.
A fisherman who helped retrieve the bodies told Hurriyet that all were without life jackets. He said that babies were among the dead.
The official Anatolia news agency said that rescuers were alerted to the sinking by fishermen and arrived at the scene of the accident to find the vessel semi-submerged.
Correspondents say that it is not clear what caused the boat to sink, although overcrowding, bad weather conditions, the poor condition of the vessel or even a collision with another boat were all possibilities.
Since the start of the civil war in Syria, thousands of migrants have been trying to reach the EU by making the treacherous sea journey from the western and southern Turkish coast.
Tens of thousands of migrants have also attempted to cross the Greek and Bulgarian borders by land, Hurriyet says.
Our correspondent says that after the deaths of hundreds of migrants off the Italian island of Lampedusa last year, southern European countries like Italy and Greece have called for a more robust response from the EU to stem the flow.
But despite more patrols by the European border agency Frontex and other naval forces, those seeking refuge in Europe continue to make the perilous journey.