Talks on forming a coalition government in Germany have collapsed, leaving Angela Merkel facing her biggest challenge in 12 years as chancellor.

The free-market liberal FDP pulled out after four weeks of talks with Mrs Merkel's CDU/CSU bloc and the Greens.

FDP leader Christian Lindner said there was "no basis of trust" between them.

What happens next is unclear, but Mrs Merkel is due to meet President Frank-Walter Steinmeier, who has the power to call snap elections.