Paris (AFP) - Germany's reintroduction of border controls Sunday in response to an overwhelming number of migrant arrivals marked the latest dramatic turn in Europe's worst refugee crisis since World War II.

More than 430,000 migrants and refugees have risked their lives since the beginning of the year making the treacherous crossing across the Mediterranean to Europe, with nearly 2,800 dying en route, according to the International Organization for Migration.

Most of those trying to reach Europe are Syrians fleeing the war at home.

Here are key dates in the crisis:

- April 23: EU leaders triple the bloc's budget for sea rescues and mull military action against human smugglers in Libya after 1,200 migrants drown in a single week off Libya. But with no UN mandate to intervene against the smugglers, a new naval task force is restricted to surveillance.

- June 3: The number of migrants trying to reach Europe through Greece is up 500 percent over 2014, EU border agency Frontex says, largely due to a surge in Syrians crossing from Turkey.

- June 17: Hungary closes its border with Serbia, which is not an EU member, and in July begins to build a fence along the length of the frontier. A razor-wire barrier is completed on August 29.

- July 20: EU leaders agree to a voluntary scheme to accept 32,256 migrants from Italy and Greece, falling short of a target of 40,000.

- July 30: A migrant in Calais, France, is the 10th to die in two months while trying to smuggle across the Channel to England. On several consecutive nights, hundreds of migrants attempt unsuccessfully to storm the Eurotunnel terminal.

- August 10: The European Commission approves 2.4 billion euros in aid for countries most affected by the migrant crisis.

- August 18: Frontex reports that the number of migrants who reached Italy between January and July tripled from the same period a year earlier to 107,000. The number of migrants arriving via Greece is around double that number.

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- August 19: Germany, the leading destination for those seeking asylum in the EU, says it expects to receive 800,000 applications by the end of 2015, four times as many as 2014.

- August 20: Macedonia declares a two-day state of emergency and temporarily closes its border with Greece after receiving a wave of migrants.

- August 23-24: Police and far-right militants clash outside a new refugee centre in Saxony, eastern Germany.

- August 27: The decomposing bodies of 71 Syrian migrants are found in an abandoned lorry in Austria. A day earlier, 52 corpses were found in the hold of a boat off Libya.

- September 2: The picture of a three-year-old Syrian boy's body, washed ashore on a Turkish beach after a migrant boat sank, prompts an outpouring of public sympathy for refugees.

- September 3: Budapest's main train station is reopened to migrants after a two-day closure and standoff. Hundreds board trains headed for the Austrian border.

- September 9: European Commission chief Jean-Claude Juncker urges member states to absorb 160,000 asylum seekers. Germany and France come out in favour of binding migrant quotas but some eastern European nations voice opposition.

- September 12: Hungary records a record 4,330 new arrivals as migrants race to reach the country before the fence is completed.

In Germany, authorities in Munich say they are stretched to the limit as they struggle to accommodate 13,000 newcomers in a single day.

- September 13: Germany reinstates passport checks at the border with Austria, in a shock U-turn on the government's earlier policy of opening its doors to Syrian refugees.

Off the Greek coast, 34 migrants -- including four babies and 11 children -- drown when their overcrowded boat capsizes.