At least 12 Syrians trying to reach Greece have drowned off Turkey after the boats they were travelling in sank.

An image of one of the victims - a young boy lying face-down on the beach - has sparked an international outcry over the human cost of the crisis.

The picture, released by a Turkish news agency, is trending worldwide on Twitter under the #KiyiyaVuranInsanlik ("humanity washed ashore") hashtag.

Thousands of migrants have died this year trying to reach Europe by sea.

The Turkish coastguard said the migrants had set off from Turkey's Bodrum peninsula for the Greek island of Kos early today, but the two boats they were in sank shortly afterwards.

Twelve bodies, including five children, were recovered. Fifteen people were said to have survived - some made it to shore with life jackets.

The coastguard said it was continuing its search for three people still missing.

The image of the young boy, shown wearing a red T-shirt and lying face-down on the beach near Bodrum, was published shortly after the incident.

While the BBC chose to publish only one photograph of the boy, in which he is being carried by a Turkish police officer and is unidentifiable, several news organisations have published more graphic images of the boy.

UK newspaper The Independent said it had decided to use the images on its website because "among the often glib words about the 'ongoing migrant crisis', it is all too easy to forget the reality of the desperate situation facing many refugees".

Despite the reaction to the image online, there has been little reaction from politicians across Europe.

Yvette Cooper, a leadership candidate for the UK's Labour Party, said the photograph showed "we cannot keep turning our backs" on the issue.

"When mothers are desperately trying to stop their babies from drowning when their boat has capsized [...] Britain needs to act."

The Turkish news agency Dogan said the boy and the rest of the group were Syrians from the besieged town of Kobane who had fled to Turkey last year to escape advancing militants from the Islamic State group.

Relatives of the victims confirmed they were from Syria.

Some 350,000 migrants have made the perilous journey to reach Europe's shores since January this year.

The IOM said more than 2,600 migrants have drowned trying to cross the Mediterranean in the same period.

Earlier this week, the Turkish government said its coastguard had rescued over 42,000 migrants in the Aegean Sea in the first five months of 2015 and more than 2,160 in the last week alone.