Germany's former Foreign Minister Guido Westerwelle is seriously ill with acute leukemia and is currently receiving treatment, his office wrote on his Facebook site. REUTERS/Denis Balibouse/File

Berlin - Germany's former foreign minister and head of the pro-business Free Democrats Guido Westerwelle is suffering from acute leukemia, the foundation he heads said Friday.

Westerwelle, 52, “is undergoing medical treatment in order to fully recover”, the head of office at the Westerwelle Foundation Alexander Vogel said in a statement.

He was Germany's top diplomat under Chancellor Angela Merkel's previous centre-right coalition until his Free Democrats suffered the party's worst-ever election defeat which saw them kicked out of parliament in last September's elections.

Merkel joined others, including Westerwelle's centre-left successor at the foreign ministry, in wishing him a speedy recovery, saying she had long known him “as a great fighter”, according to a spokesman.

Westerwelle was also FDP head from 2001 until 2011.

Several months ago, he established the Westerwelle Foundation for International Understanding aimed at strengthening democracy by promoting economic development.