Nato will send three warships to the Aegean Sea "without delay" in a bid to tackle people smugglers preying on fleeing migrants. People smugglers are known to set use various types of vessels, in various states of repair, to ferry over desperate people from Turkey to Greece as migrants seek safe haven in the EU.

Migrants often use Turkey as a transit country en route to northern Europe, with many coming from war-torn Syria, Iraq and Afghanistan or impoverished parts of Africa. Estimates suggest that more than a million people arrived in Europe in 2015 – the largest movement since World War II.

In Turkey and elsewhere, migrants have been charged huge sums by traffickers to help them cross from the mainland to the Greek islands on sometimes rickety and poorly-maintained vessels.

So far this year, an estimated 70,000 people have crossed the sea, with more than 300 perishing, according to the International Organisation for Migration (IOM). Nato confirmed that they will send the warships from to "start maritime surveillance activities" from Cyprus. They could be operational in 24 hours, with details being discussed by generals as they travel.

NATO Secretary General Jens Stoltenberg told a news conference that refugees were not the targets of the mission. He said: "This is not about stopping and pushing back [refugees]...but about critical surveillance to help counter human trafficking and criminal networks".

The new mission is planning to send migrants back to Turkey rather than to Greece, as the current EU maritime mission does. UK defence minister Michael Fallon said this marked a significant change in policy. He said: "They won't be taken to Greece and that's a crucial difference."

NATO also announced plans to monitor the Turkey-Syria land border for people-smugglers and US Defence Secretary Ashton Carter said: "There is now a criminal syndicate which is exploiting these poor people. Targeting that is the greatest way an effect could be had."

The new Nato plans come amid the trial of two alleged people smugglers who go on trial for causing the death of Syrian toddler Alan Kurdi, whose death sparked global grief. Muwafaka Alabash and Asem Alfrhad, both from Syria, are accused of smuggling migrants and causing the deaths of five people, including Alan, his five-year-old brother Galip and their mother Rihan.