HANOVER (AFP) - United States President Barack Obama called on Europe to carry more of the shared burden for security, directly challenging the continent's leaders while on a visit to Germany on Monday (April 25).

"Europe has sometimes been complacent about its own defence," Mr Obama said bluntly.

Underlining that Nato has to "bolster our frontline allies in Poland, in Romania and in Baltic states" while also "meet the threat of its southern flank", Mr Obama urged members of the alliance to increase their defence capacities.

"That's why every Nato member should be contributing its full share of 2 per cent of GDP (gross domestic product) towards our common security. Something that doesn't always happen," he said.

Mr Obama's host country and Europe's economic heavyweight Germany has been frequently criticised for spending well below the target on defence capabilities.