Refugee crisis: Drone footage reveals sprawling camp at Greece-Macedonia borderIBTimes UK

As many as 900 migrants may have drowned in the Mediterranean while attempting to reach Europe from Africa over the last seven days, according to Médecins Sans Frontières (MSF). An estimate by the United Nations refugee agency (UNHCR) puts the death toll slightly lower, at about 700. Around 13,000 migrants have been rescued over the same period (22-29 May 2016).

Dramatic footage of migrants swimming for their lives after a boat overturned on Wednesday, 25 May, was broadcast around the world. Initially, it seemed the death toll in that incident was five, but it is now thought that as many as 100 may have perished, many of them still trapped beneath the boat. On Thursday, another boat overturned after leaving Sabratha in Libya leaving up to 550 dead. On Friday, at least 45 died and an unknown number are still missing after another shipwreck.

Rising numbers of people are trying to reach Europe as the weather improves and all three of the incidents involved boats attempting to travel from the African coast. This is now the preferred route as the shorter route between Turkey and Greece is better policed. However, the route is also much longer and therefore more dangerous.

On Saturday, 28 May, some 600 migrants had to be rescued by EU boats. The UK announced it will be sending a navy warship to patrol the waters off Libya.

The UNHCR estimates more than one million refugees arrived in Europe in 2015, and at least 3,771 died or disappeared while trying to make the journey. Many of the migrants are fleeing the war in Syria and many more are from impoverished regions including parts of Africa and the Middle East.

The scale of the crisis is beginning to have an impact both on Europe's resources and its unity. The issue of migration is playing a major part in the debate on the EU referendum on 23 June.